JavaScript Syntax

Syntax is the set of rules for writing correct JavaScript. A JavaScript program is a list of statements, and each statement is an instruction for the computer.

let price = 100;
let tax = 18;
let total = price + tax;
console.log(total);

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Rules to remember

• Semicolons: a statement normally ends with ;. JavaScript can often add it for you, but write it to avoid surprises.
• Case sensitive: name, Name and NAME are three different variables.
• Whitespace: extra spaces and new lines are ignored. Use them to keep code readable.
• Code blocks: statements that go together are wrapped in curly braces { }.
• Strings are written in single quotes, double quotes or backticks.

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Identifiers (names)

The names of variables and functions are called identifiers.

• They can have letters, digits, _ and $.
• They cannot start with a digit.
• They cannot be a keyword like let, if or function.

let firstName = "Robin";     // camelCase, the usual style
let _count = 0;
let $price = 99;
// let 1name = "x";         // wrong: starts with a digit

The common style is camelCase: first word in small letters, then every new word with a capital letter, like totalPrice.

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Case sensitivity

let age = 20;
console.log(age);
console.log(Age);

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Summary

• A program is a list of statements, usually ending with a semicolon.
• JavaScript is case sensitive.
• Use camelCase names that do not start with a digit.
• Next: JavaScript Comments.

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