Method chaining in Javascript

Rahul Chaudhary — Tue, 13 Sep 2022 05:30:47 +0000

NOTE: In method chaining we return this

Method Chaining example using ES6 class

//method chaining using class object
class Calculator {
    constructor() {
        this.value = 0;
    }
    add(x) {
        this.value += x;
        return this;
    }
    sub(x) {
        this.value -= x;
        return this;
    }
    mul(x) {
        this.value *= x;
        return this;
    }
}

const obj = new Calculator();
obj.add(10).add(10).mul(2).value;

Method chaining example using javascript object shorthand

//method chaining using object shorthand
let operations = {
    arrayValue: [],
    insert: function (x) {
        this.arrayValue.push(x);
        return this;
    },
    remove: function () {
        this.arrayValue.pop();
        return this;
    },
    filterMatching: function (x) {
        this.arrayValue = this.arrayValue.filter((e) => e === x);
        return this;
    },
};

operations.insert(1).insert(2).insert(3).remove().filterMatching(1).arrayValue;

Guess the output

Rahul Chaudhary — Fri, 19 Nov 2021 02:50:34 +0000

var a = 2;
if (true) {
var a = 5;
console.log(a) // 5
}
console.log(a) // 5

I'm new to Javascript, can anyone tell why it printed 5 in below console statement

Forem: Rahul Chaudhary

Method chaining in Javascript

Guess the output