JavaScript property_exists

Checks if the object or class has a property

function property_exists (cls, prop) {
    // Checks if the object or class has a property  
    // 
    // version: 1109.2015
    // discuss at: http://phpjs.org/functions/property_exists    // +   original by: Brett Zamir (http://brett-zamir.me)
    // *     example 1: function class_a () {this.prop1 = 'one'};
    // *     example 1: var instance_a = new class_a();
    // *     example 1: property_exists(instance_a, 'prop1');
    // *     returns 1: true    // *     example 2: function class_a () {this.prop1 = 'one'};
    // *     example 2: var instance_a = new class_a();
    // *     example 2: property_exists(instance_a, 'prop2');
    // *     returns 2: false
    cls = (typeof cls === 'string') ? this.window[cls] : cls; 
    if (typeof cls === 'function' && cls.toSource && cls.toSource().match(new RegExp('this\\.' + prop + '\\s'))) {
        // Hackish and non-standard but can probably detect if setting
        // the property (we don't want to test by instantiating as that
        // may have side-effects)        return true;
    }
 
    return (cls[prop] !== undefined && typeof cls[prop] !== 'function') || (cls.prototype !== undefined && cls.prototype[prop] !== undefined && typeof cls.prototype[prop] !== 'function') || (cls.constructor && cls.constructor[prop] !== undefined && typeof cls.constructor[prop] !== 'function');
}

external links: original PHP docs | raw js source

Examples

» Example 1

Running

1
2
3

function class_a () {this.prop1 = 'one'};
var instance_a = new class_a();
property_exists(instance_a, 'prop1');

Should return

true

» Example 2

Running

1
2
3

function class_a () {this.prop1 = 'one'};
var instance_a = new class_a();
property_exists(instance_a, 'prop2');

Should return

false

Dependencies

No dependencies, you can use this function standalone.

Open syntax issues

php.js uses JsLint to help us keep our code consistent and prevent some common bugs.

Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.

Authors

Thanks to the following developers, you get to have property_exists goodness in JavaScript.

Brett Zamir ( original )

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