+= (Add Assign)
+= (Add Assign) is a JavaScript function in the Operators category. Adds and assigns. The syntax is x += value. A typical example: let x=5; x += 3 // 8. A close sibling is + (Addition), which adds numbers or concatenates strings. A close sibling is - (Subtraction), which subtracts numbers. A close sibling is * (Multiplication), which multiplies numbers. A close sibling is === (Strict Equality), which strict equality. More about this category: Arithmetic, comparison, logical, bitwise operators. Related Operators methods: + (Addition), - (Subtraction), * (Multiplication), === (Strict Equality), && (Logical AND), || (Logical OR), ?? (Nullish Coalescing), ?. (Optional Chaining). This page is part of the free JS Reference documentation covering 1027+ methods, each with syntax, parameters, return values, examples, and common pitfalls. You can try += (Add Assign) immediately in the JavaScript playground, look up unfamiliar terms in the glossary, or return to the JS Reference homepage.