Question

61

Check if object has a set of properties in javascript

rated 0 times [ 63] [ 2] / answers: 1 / hits: 23910 / 11 Years ago, sat, december 14, 2013, 12:00:00

Let's say I have an object named a, how could I check that a has a specific list of multiple properties in shorthand, I think it can be done using in logical operator,

Something like this:

var a = {prop1:{},prop2:{},prop3:{}};

if ({1:prop1,2:prop2,3:prop3} in a)

    console.log(a has these properties:'prop1, prop2 and prop3');

EDIT

If plain javascript can't help, jQuery will do, but i prefer javascript

EDIT2

Portability is the privilege

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skyler

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answered 11 Years ago michelecarissab · Accepted Answer

The simplest away is to use a conventional &&:

if (prop1 in a && prop2 in a && prop3 in a) 

    console.log(a has these properties:'prop1, prop2 and prop3');

This isn't a 'shorthand', but it's not that much longer than what you've proposed.

You can also place the property names you want to test in an array and use the every method:

var propertiesToTest = [prop1, prop2, prop3];

if (propertiesToTest.every(function(x) { return x in a; })) 

    console.log(a has these properties:'prop1, prop2 and prop3');

Note however, that this was introduced in ECMAScript 5, so it is not available on some older browsers. If this is a concern, you can provide your own version of it. Here's the implementation from MDN:

if (!Array.prototype.every) {

  Array.prototype.every = function(fun /*, thisp */) {

    'use strict';

    var t, len, i, thisp;



    if (this == null) {

      throw new TypeError();

    }



    t = Object(this);

    len = t.length >>> 0;

    if (typeof fun !== 'function') {

        throw new TypeError();

    }



    thisp = arguments[1];

    for (i = 0; i < len; i++) {

      if (i in t && !fun.call(thisp, t[i], i, t)) {

        return false;

      }

    }



    return true;

  };

}