Get JavaScript object from array of objects by value of property

jsObjects.find(x => x.b === 6)

From MDN:

The find() method returns a value in the array, if an element in the array satisfies the provided testing function. Otherwise undefined is returned.

Side note: methods like find() and arrow functions are not supported by older browsers (like IE), so if you want to support these browsers, you should transpile your code using Babel.

I don't know why you are against a for loop (presumably you meant a for loop, not specifically for..in), they are fast and easy to read. Anyhow, here's some options.

For loop:

function getByValue(arr, value) {

  for (var i=0, iLen=arr.length; i<iLen; i++) {

    if (arr[i].b == value) return arr[i];
  }
}

.filter

function getByValue2(arr, value) {

  var result  = arr.filter(function(o){return o.b == value;} );

  return result? result[0] : null; // or undefined

}

.forEach

function getByValue3(arr, value) {

  var result = [];

  arr.forEach(function(o){if (o.b == value) result.push(o);} );

  return result? result[0] : null; // or undefined

}

If, on the other hand you really did mean for..in and want to find an object with any property with a value of 6, then you must use for..in unless you pass the names to check. e.g.

function getByValue4(arr, value) {
  var o;

  for (var i=0, iLen=arr.length; i<iLen; i++) {
    o = arr[i];

    for (var p in o) {
      if (o.hasOwnProperty(p) && o[p] == value) {
        return o;
      }
    }
  }
}

Try Array filter method for filter the array of objects with property.

var jsObjects = [
   {a: 1, b: 2}, 
   {a: 3, b: 4}, 
   {a: 5, b: 6}, 
   {a: 7, b: 8}
];

using array filter method:

var filterObj = jsObjects.filter(function(e) {
  return e.b == 6;
});

using for in loop :

for (var i in jsObjects) {
  if (jsObjects[i].b == 6) {
    console.log(jsObjects[i]); // {a: 5, b: 6}
  }
}

Working fiddle : https://jsfiddle.net/uq9n9g77/

OK, there are few ways to do that, but let's start with the simplest one and latest approach to do this, this function is called find().

Just be careful when you using find to as even IE11 dosn't support it, so it needs to be transpiled...

so you have this object as you said:

var jsObjects = [
   {a: 1, b: 2}, 
   {a: 3, b: 4}, 
   {a: 5, b: 6}, 
   {a: 7, b: 8}
];

and you can write a function and get it like this:

function filterValue(obj, key, value) {
  return obj.find(function(v){ return v[key] === value});
}

and use the function like this:

filterValue(jsObjects, "b", 6); //{a: 5, b: 6}

Also in ES6 for even shortened version:

const filterValue = (obj, key, value)=> obj.find(v => v[key] === value);

This method only return the first value which match..., for better result and browser support, you can use filter:

const filterValue = (obj, key, value)=> obj.filter(v => v[key] === value);

and we will return [{a: 5, b: 6}]...

This method will return an array instead...

You simpley use for loop as well, create a function like this:

function filteredArray(arr, key, value) {
  const newArray = [];
  for(i=0, l=arr.length; i<l; i++) {
    if(arr[i][key] === value) {
      newArray.push(arr[i]);
    }
  }
 return newArray;
}

and call it like this:

filteredArray(jsObjects, "b", 6); //[{a: 5, b: 6}]

Using underscore.js:

var foundObject = _.findWhere(jsObjects, {b: 6});