Javascript - object with key value pair, where value is an array

Question

I'm trying to create an object where there is a key value pair, and the value is an array.

i.e:

foo = {'key1':['val1','val2'], 'key2':['v3','v4']};

Is this possible in pure JS?

e.g.

var foo = {};
foo['key1'] = ['keyOneVal1'];
foo['key1'] = ['keyOneVal2'];

but as you may have guessed, this just overwrites the keyOneVal1.

I've also tried

var foo = {};
foo['key1'].push('k1v1');
foo['key1'].push('k1v2');

but couldn't get it working in a jsfiddle.

EDIT:

Okay heard you guys loud and clear. This object will not be initialized with an starting key, it's dynamically inserted based on time. So in the end the object will look more like

foo = {'time1':['a','b'], 'time2':['c','d','e','f'], 'time3':['y','y']};

Are you trying to do it dynamically? Your "example" is perfectly valid. — Evan Davis
– Evan Davis, Commented Dec 16, 2014 at 20:49

Justin Niessner · Accepted Answer · 2014-12-16 20:50:05Z

6

It's very possible. Your second example is the correct way to do it. You're just missing the initializer:

var foo = {};
foo['key1'] = [];
foo['key1'].push('k1v1');
foo['key1'].push('k1v2');

for(var i = 0; i < foo['key1'].length; i++) {
  document.write(foo['key1'][i] + '<br />');
}

answered Dec 16, 2014 at 20:50

Justin Niessner

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3 Comments

Justin Niessner Over a year ago

You need the initializer because foo['key1'] isn't an array. It's undefined until you initialize it as an empty array.

Bhojendra Rauniyar Over a year ago

and what's this so ? foo = {'key1':['val1','val2'], 'key2':['v3','v4']};

Justin Niessner Over a year ago

@Bhojendra-C-LinkNepal - That's the result that the OP is hoping to get as a result of their statements, not the starting point.

brso05 · Accepted Answer · 2014-12-16 20:49:20Z

2

Try something like this make sure you declare key1:

var foo = {"key1" : []};
foo['key1'].push('k1v1');
foo['key1'].push('k1v2');

answered Dec 16, 2014 at 20:49

brso05

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Comments

Chop · Accepted Answer · 2014-12-16 20:50:13Z

1

It can be done like this

var foo = {"key":[]}
foo["key"].push("val1")
foo["key"].push("val2")

answered Dec 16, 2014 at 20:50

Chop

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