Determine if the object has a property and value in javascript

Question

I wanted to check if the an object has a property of something and its value is equal to a certain value.

var test = [{name : "joey", age: 15}, {name: "hell", age: 12}]

There you go, an array of objects, now I wanted to search inside the object and return true if the object contains what I wanted.

I tried to do it like this:

Object.prototype.inObject = function(key, value) {
if (this.hasOwnProperty(key) && this[key] === value) {
  return true
};
return false;
};

This works, but not in an array. How do I do that?

Answer 1

Use the some Array method to test your function for each value of the array:

function hasValue(obj, key, value) {
    return obj.hasOwnProperty(key) && obj[key] === value;
}
var test = [{name : "joey", age: 15}, {name: "hell", age: 12}]
console.log(test.some(function(boy) { return hasValue(boy, "age", 12); }));
// => true - there is a twelve-year-old boy in the array

Btw, don't extend Object.prototype.

Answer 2

-- for the property --

if(prop in Obj)  
//or
Obj.hasOwnProperty(prop)

-- for the value ---

Using "Object.prototype.hasValue = ..." will be FATAL for js but Object.defineProperty let you define properties with enumerable:false (default)

Object.defineProperty(Object.prototype,"hasValue",{
   value : function (obj){
              var $=this;
              for( prop in $ ){
                  if( $[prop] === obj ) return prop;
              }
              return false;
           }
});

just for experiment test if a NodeList has an Element

var NL=document.QuerySelectorAll("[atr_name]"),
    EL= document.getElementById("an_id");
console.log( NL.hasValue(EL) )  

// if false then #an_id has not atr_name