Javascript function optional parameters

Question

I have a simple function that updates the values of an object. Currently, the function takes in 3 parameters to updated the object. I would like an optional fourth parameter that will accept an array of objects (array) and change the values for all the objects in the array. If the fourth parameter is provided I would like to ignore the others. What is the best way to do this? Thanks

var myObj = {myKey : 0}
var obj1 = {myKey : 0}
var obj2 = {myKey : 0}
var array = [{obj: obj1, key: 'myKey1', value: 1},{obj: obj2, key: 'myKey2', value: 2}]

function changeRule(obj, key, value) {
        obj[key] = value
    },  

changeRule(myObj, 'myKey', 1)

You can just add a condition in your function that checks for the value of the fourth parameter and if it's not undefined just ignore the others. — Gilad Bar
– Gilad Bar, Commented Nov 27, 2018 at 15:38

brk · Accepted Answer · 2018-11-27 15:40:19Z

2

Check if 4th parameter is undefined and if it is an array

var myObj = {
  myKey: 0
}
var obj1 = {
  myKey: 0
}
var obj2 = {
  myKey: 0
}
var array = [{
  obj: obj1,
  key: 'myKey1',
  value: 1
}, {
  obj: obj2,
  key: 'myKey2',
  value: 2
}]

function changeRule(obj, key, value, array) {
  if (array! == undefined && Array.isArray(array)) {
    // rest of the code to change the object properties
    return;
  }
  obj[key] = value
},

changeRule(myObj, 'myKey', 1, array)

answered Nov 27, 2018 at 15:40

brk

50.3k10 gold badges59 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

lukechambers91 Over a year ago

If I do what you mentioned then changeRule(array) would not work right? I have to have the other parameters right?

lukechambers91 Over a year ago

Should just have two functions? One which accepts and array and another which accepts the parameters.

brk Over a year ago

You can still do that by tweaking the function and checking argument length. But in that case what about if the user does not pass an array but call the function with only myObj?

AbhaY · Accepted Answer · 2018-11-27 16:42:34Z

Check if it works for your problem statement, copy code and run in developer console, it won't run here properly.

var obj1 = {
  myKey: 0
};
var obj2 = {
  myKey: 0
};
var array = [{
  obj: 'obj1',
  key: 'myKey',
  value: 1
}, {
  obj: 'obj2',
  key: 'myKey',
  value: 2
}]

function changeRule(objOrArray, key, value) {
  if (objOrArray !== undefined && Array.isArray(objOrArray)) {
    //code that would change value of all objects according to data in array
    objOrArray.forEach(_obj => {
      eval(_obj.obj)[_obj.key] = _obj.value;
    });
    return;
  } else if (objOrArray !== undefined && key !== undefined && value !== undefined) {
    objOrArray[key] = value;
  } else {
    console.warn('param1 must be an Array, or Object with param2(key) & param3(value)');
  }
  return;
}

changeRule(array);

console.log(obj1, obj2);

Note: I have made a change in the structure of array of objects. (obj name is should be a string.)

Why pass the object name as a string that you have to eval() later, when you can just pass the object itself?
@lukechambers91 you are right, it seems unnecessary, my bad. BTW thanks for pointing out.

lukechambers91 · Accepted Answer · 2018-11-27 17:52:44Z

This is what I went with. Thanks for all the help! I learned a lot from this post.

var myObj = {
      myKey: 0
    }
    var obj1 = {
      myKey1: 0
    }
    var obj2 = {
      myKey2: 0
    }
    var array = [{
      obj: obj1,
      key: 'myKey1',
      value: 1
    }, {
      obj: obj2,
      key: 'myKey2',
      value: 2
    }]
    
    function changeRule() {
            if (arguments.length == 1 && Array.isArray(arguments[0])) {
                arguments[0].forEach(e => {
                    e.obj[e.key] = e.value
                });
              } else if (arguments.length == 3 && typeof arguments[0] == "object" && typeof arguments[1] == "string" && typeof arguments[2] == "number") {
                arguments[0][arguments[1]] = arguments[2]
              } else {
                  return "Unacceptable input parameters"
              }
        }
    console.log(obj1)
    console.log("------------------------")
    changeRule(array);
    console.log(obj1)

Collectives™ on Stack Overflow

Javascript function optional parameters

3 Answers 3

3 Comments

2 Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

2 Comments

Comments

Related