JS-016
Visual JavaScript guide to Expression: Learn what an expression is and why every expression produces a value
Beginner3 min~3 min read#expression#values#operators

Expression

Produces a value

Goal

Learn what an expression is and why every expression produces a value.

Explanation

  • An expression is any piece of code that evaluates to a single value.
  • An expression can be a math calculation, a comparison, or string concatenation.
  • JavaScript first evaluates the expression, then uses the resulting value.
  • That value can be a number, string, boolean, or any other type.
  • Almost every program is built from a large number of expressions.

Analogy

An expression is like a calculator. You enter a calculation and always get a ready result.

Code

console.log(5 + 3);
console.log("Hi" + "!");
console.log(10 > 3);

Result: 8 Hi! true

Common mistake

Beginners often think an expression must be math. In reality, any code that produces a value is an expression.

Remember

  • ✦ An expression always returns a value.
  • ✦ The result of an expression can be used further in the program.
  • ✦ 5 + 3, "Hi" + "!", and 10 > 3 are expressions.

Quick Quiz

What does an expression do?

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