For..In loops in JavaScript - key value pairs
for (var k in target){ if (target.hasOwnProperty(k)) { alert("Key is " + k + ", value is " + target[k]); }}hasOwnProperty is used to check if your target really has that property, rather than having inherited it from its prototype. A bit simpler would be:
for (var k in target){ if (typeof target[k] !== 'function') { alert("Key is " + k + ", value is" + target[k]); }}It just checks that k is not a method (as if target is array you'll get a lot of methods alerted, e.g. indexOf, push, pop,etc.)
If you can use ES6 natively or with Babel (js compiler) then you could do the following:
const test = {a: 1, b: 2, c: 3};for (const [key, value] of Object.entries(test)) { console.log(key, value);}Which will print out this output:
a 1b 2c 3The Object.entries() method returns an array of a given object's own enumerable property [key, value] pairs, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).
- Object.entries documentation
- for...of documentation
- Destructuring assignment documentation
- Enumerability and ownership of properties documentation
Hope it helps! =)
No one has mentioned Object.keys so I'll mention it.
Object.keys(obj).forEach(function (key) { // do something with obj[key]});