CODEWITHSUNDEEP
javascriptjqueryobjectpropertiesoperators
Ben
Ben

Reputation: 4297

Check if object has a set of properties in javascript

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

Upvotes: 18

Views: 26917

Answers (6)

Mark Tyers
Mark Tyers

Reputation: 3269

Slightly more elegant use of the Object.every() prototype function to include try-catch:

try {
  const required = ['prop1', 'prop2', 'prop3']
  const data = {prop1: 'hello', prop2: 'world', prop3: 'bad'}
  if (!required.every( x => x in data )) throw new Error('missing property')
  console.log('all properties found')
} catch(err) {
  console.log(err.message)
}
``

Upvotes: 1

p.s.w.g
p.s.w.g

Reputation: 149078

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;
  };
}

Upvotes: 37

Ringo
Ringo

Reputation: 3967

I think it's good to try it:

/* Create an object class */
var obj = function(){ this.attributes = new Array(); }
obj.prototype.addProp = function(value){ this.attributes.push(new attribute(value)); }
obj.prototype.hasProp = function(value){ 
    for(var i = 0; i < this.attributes.length; i++){ 
      if(value == this.attributes[i].value) return true; } return false; }
function attribute(value){
    this.value = value;
}
/* Testing object has some value*/
var ob = new obj();
ob.addProp('1');
ob.addProp('2');
ob.addProp('3');
 //* check value index
//alert(ob.attributes[0].value);
 //* check if ob has prop
alert(ob.hasProp('1'));

Here is DEMO

Upvotes: 0

Dexygen
Dexygen

Reputation: 12561

This is where the underscore.js library really shines. For instance it provides an already poly-filled every() method as suggested in a comment to p.s.w.g.'s answer: http://underscorejs.org/#every

But there's more than one way to do it; the following, while more verbose, may also suit your needs, and exposes you to more of what underscore can do (e.g. _.keys and _.intersection)

var a = {prop1:{},prop2:{},prop3:{}};
var requiredProps = ['prop1', 'prop2', 'prop3'];
var inBoth = _.intersection(_.keys(a), requiredProps);
if (inBoth.length === requiredProps.length) {
    //code
}

Upvotes: 7

Sachin Jain
Sachin Jain

Reputation: 21842

Use Array.reduce like this:

var testProps = ['prop1', 'prop2', 'prop3'];
var a = {prop1:{},prop2:{},prop3:{}};

var result = testProps.reduce(function(i,j) { return i && j in a }, true);
console.log(result);

Upvotes: 6

StackSlave
StackSlave

Reputation: 10617

Like this:

var testProps = ['prop1', 'prop2', 'prop3', 'prop4'];
var num = -1, outA;
for(var i in a){
  if(i === testProps[++num])outA[num] = i;
}
console.log('properties in a: '+outA.join(', '));

Upvotes: 1

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