How to get all the values associated with an object in array?

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Just filter the values and map the desired ones.

array.filter allows you to filter items of an array with a condition, so using i => i.name === 'test0' will return a new array where only the values with name ‘test0’ are acquired. Finally, using map you create a new array, whose values are the result of the callback function provided. So, using map(i => i.value) will return the property .value of each (filtered) object.

If you’re expecting the values to be numeric, remember to cast them to integers.

var array = [
    { name:"test0", value:"0" },
    { name:"test1", value:"1" },
    { name:"test2", value:"2" },
    { name:"test0", value:"3" },
    { name:"test0", value:"4" }
];

var res = array.filter(i => i.name === 'test0').map(i => i.value);
console.log(res);

Otherwise, you can do that in a single shot with reduce:

var array = [
    { name:"test0", value:"0" },
    { name:"test1", value:"1" },
    { name:"test2", value:"2" },
    { name:"test0", value:"3" },
    { name:"test0", value:"4" }
];

var res = array.reduce((a,b) => {
  return b.name === 'test0' && a.push(+b.value), a;
}, []);
console.log(res);

In this last example, the values are casted to integers using the unary operator (+).

Finally, as requested, here is another approach not relying on any array prototype:

var array = [
    { name:"test0", value:"0" },
    { name:"test1", value:"1" },
    { name:"test2", value:"2" },
    { name:"test0", value:"3" },
    { name:"test0", value:"4" }
];

// init a new empty array.
var res = [];
for (var i = 0; i < array.length; i++) {
  var item = array[i]; // not mandatory but easy enough to read: acquire the current looped value.
  if (item.name === 'test0') { // if the looped item name is 'test0', join the if.
    res.push(Number(item.value)); // if so, push the item's value, and cast it to a number (using Number).
  }
}
console.log(res); // log the result.

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