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3) Learn to Crawl Before You Can Run Lesson

JavaScript Syntax: Case-Sensitivity

3 min to complete · By Ian Currie

In this lesson you will learn about case-sensitivity and how JavaScript treats different cases.

Is JavaScript Case-Sensitive?

Yes, JavaScript is case-sensitive.

let sum = 5;
let sum = 7; // Uncaught SyntaxError: Identifier 'sum' has already been declared
let Sum = 10;
let SUm = 15;
let SUM = 20;

console.log(sum); // 5
console.log(Sum); // 10
console.log(SUm); // 15
console.log(SUM); // 20

As this example shows, you can have multiple variables with the same letters that differ only by their case and these are considered different variables.

Summary: JavaScript Syntax - Case-Sensitive

  • You've guessed it: JavaScript is case-sensitive ;)