Revisions to Check if a value is an object in JavaScript

edited body

Source Link

edited Aug 10, 2019 at 10:07

274
2
6

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['BigInt64Array']=true;
    arrayTypes['BigUInt64Array']=true;arrayTypes['BigUint64Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['BigInt64Array']=true;
    arrayTypes['BigUInt64Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['BigInt64Array']=true;
    arrayTypes['BigUint64Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Added: BigInt64Array, BigUInt64Array

Source Link

edited Aug 10, 2019 at 10:01

c7x43t

274
2
6

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['BigInt64Array']=true;
    arrayTypes['BigUInt64Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['BigInt64Array']=true;
    arrayTypes['BigUInt64Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

also checking for null values as they would throw exceptions

Source Link

edit approved Jan 31, 2019 at 13:56

Caina Santos

969
1
9
16

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

Since there seems a lot of confusion about how to handle this problem correctly, I'll leave my 2 cents (this answer is spec compliant and produces correct results under all circumstances):

Testing for primitives: undefined null boolean string number

function isPrimitive(o){return typeof o!=='object'||null}

An object is not a primitive:

function isObject(o){return !isPrimitive(o)}

Or alternatively:

function isObject(o){return o instanceof Object}
function isPrimitive(o){return !isObject(o)}

Testing for any Array:

const isArray=(function(){
    const arrayTypes=Object.create(null);
    arrayTypes['Array']=true;
    arrayTypes['Int8Array']=true;
    arrayTypes['Uint8Array']=true;
    arrayTypes['Uint8ClampedArray']=true;
    arrayTypes['Int16Array']=true;
    arrayTypes['Uint16Array']=true;
    arrayTypes['Int32Array']=true;
    arrayTypes['Uint32Array']=true;
    arrayTypes['Float32Array']=true;
    arrayTypes['Float64Array']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!!arrayTypes[o.constructor.name];
    }
}());

Testing for object excluding: Date RegExp Boolean Number String Function any Array

const isObjectStrict=(function(){
    const nativeTypes=Object.create(null);
    nativeTypes['Date']=true;
    nativeTypes['RegExp']=true;
    nativeTypes['Boolean']=true;
    nativeTypes['Number']=true;
    nativeTypes['String']=true;
    nativeTypes['Function']=true;
    return function(o){
        if (!o) return false;
        return !isPrimitive(o)&&!isArray(o)&&!nativeTypes[o.constructor.name];
    }
}());

deleted 65 characters in body

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edited Nov 13, 2018 at 12:19

c7x43t

274
2
6

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added 99 characters in body

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edited Nov 12, 2018 at 16:38

c7x43t

274
2
6

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answered Nov 12, 2018 at 14:06

c7x43t

274
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