How can I merge properties of two JavaScript objects dynamically

Questions

I need to be able to merge two (very simple) JavaScript objects at runtime. For example I d like to:

var obj1 = { food:  pizza , car:  ford  }
var obj2 = { animal:  dog  }

obj1.merge(obj2);

//obj1 now has three properties: food, car, and animal

Does anyone have a script for this or know of a built in way to do this? I do not need recursion, and I do not need to merge functions, just methods on flat objects.

Answers

  ECMAScript 2015 (ES6) Standard Method   

/* For the case in question, you would do: */
Object.assign(obj1, obj2);

/** There s no limit to the number of objects you can merge.
 *  All objects get merged into the first object. 
 *  Only the object in the first argument is mutated and returned.
 *  Later properties overwrite earlier properties with the same name. */
const allRules = Object.assign({}, obj1, obj2, obj3, etc);

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#Browser_compatibility https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#Browser_compatibility

---

  Method for ES5 and Earlier   

for (var attrname in obj2) { obj1[attrname] = obj2[attrname]; }

Note that this will simply add all attributes of obj2 to obj1 which might not be what you want if you still want to use the unmodified obj1.

If you re using a framework that craps all over your prototypes then you have to get fancier with checks like hasOwnProperty, but that code will work for 99% of cases.

Example function:

/**
 * Overwrites obj1 s values with obj2 s and adds obj2 s if non existent in obj1
 * @param obj1
 * @param obj2
 * @returns obj3 a new object based on obj1 and obj2
 */
function merge_options(obj1,obj2){
    var obj3 = {};
    for (var attrname in obj1) { obj3[attrname] = obj1[attrname]; }
    for (var attrname in obj2) { obj3[attrname] = obj2[attrname]; }
    return obj3;
}

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/171251/how-can-i-merge-properties-of-two-javascript-objects-dynamically

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