Search⌘ K
AI Features
Home
Courses
Complete JavaScript Course: Build a Real World App from Scratch

Expressions

Explore how JavaScript expressions are formed by combining variables, values, and operators to produce values. Understand operator precedence, evaluation, and how template literals embed expressions within strings for dynamic content.

We'll cover the following...

An expression is a piece of code that produces a value. An expression is created by combining variables, values and operators. Every expression has a value and thus a type. Calculating an expression’s value is called evaluation. During evaluation, variables are replaced by their values.

Javascript (babel-node)
// 3 is an expression whose value is 3
const c = 3;
// c is an expression whose value is the value of c (3 here)
let d = c;
// (d + 1) is an expression whose value is d's + 1 (4 here)
d = d + 1; // d now contains the value 4
console.log(d); // Show 4

Operator priority inside an expression is the same as in math. However, an expression can integrate parenthesis that modify these priorities.

Javascript (babel-node)
let e = 3 + 2 * 4; // e contains 11 (3 + 8)
console.log(e);
e = (3 + 2) * 4;   // e contains 20 (5 * 4)
console.log(e);

It is possible to include expressions in a string by using backticks (`) to delimit the string. Such a string is called a template literal. Inside a template literal, expressions are identified by the ${expression} syntax.

This is often used to create strings containing the values of some variables.

Javascript (babel-node)
const country = "France";
console.log(`I live in ${country}`); // Show "I live in France"
const x = 3;
const y = 7;
console.log(`${x} + ${y} = ${x + y}`); // Show "3 + 7 = 10"