Lot of changes are happening in JavaScript. ES6 shifted standard of JavaScript language to one level up. const is one of the concept ,that is introduced as apart of ES6 standard. Those, who came from the C or Java , they have different meaning for this. const in JavaScript means “one-time assignment” . It doesn’t mean constant. It means you can assign the a variable or object once. But doesn’t mean immutable. The immutable concept require explanations. We will understand in below examples.