Swap Two Numbers
Program to swap values of two variables
JavaScript Swap Two Numbers Program
This program helps you to learn the fundamental structure and syntax of JavaScript programming.
// Method 1: Using a temporary variable
let a = 5;
let b = 10;
console.log("Before swap: a =", a, ", b =", b);
let temp = a;
a = b;
b = temp;
console.log("After swap: a =", a, ", b =", b);
// Method 2: Using destructuring (ES6 - Modern approach)
let x = 5;
let y = 10;
console.log("Before swap: x =", x, ", y =", y);
[x, y] = [y, x];
console.log("After swap: x =", x, ", y =", y);
// Method 3: Using arithmetic (without temp variable)
let p = 5;
let q = 10;
console.log("Before swap: p =", p, ", q =", q);
p = p + q;
q = p - q;
p = p - q;
console.log("After swap: p =", p, ", q =", q);Before swap: a = 5 , b = 10 After swap: a = 10 , b = 5 Before swap: x = 5 , y = 10 After swap: x = 10 , y = 5 Before swap: p = 5 , q = 10 After swap: p = 10 , q = 5
Understanding Swap Two Numbers
This program demonstrates different methods to swap two variable values in JavaScript.
Method 1: Temporary Variable
The most straightforward and readable approach:
Pros:
Cons:
Method 2: Destructuring Assignment (ES6)
Modern JavaScript feature that's clean and elegant:
[a, b] = [b, a];
How it works:
Pros:
Cons:
Method 3: Arithmetic Swap
Uses addition and subtraction (only works with numbers):
a = a + b;
b = a - b;
a = a - b;
Pros:
Cons:
When to Use:
-
Method 1:
General purpose, most readable
-
Method 2:
Modern code, any data type
-
Method 3:
Only for numbers, when memory is critical
Let us now understand every line and the components of the above program.
Note: To write and run JavaScript programs, you need to set up the local environment on your computer. Refer to the complete article Setting up JavaScript Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your JavaScript programs.
Practical Learning Notes for Swap Two Numbers
This JavaScript program is part of the "Basic Programs" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.
A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.
For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.