Default parameters

Default function parameters allow formal parameters to be initialized with default values if no value or undefined is passed.

function multiply(value1=1, value2=1) { return value1 * value2; } console.log(multiply(4)); // 4

The above default parameter code is equivalent to the following code.

function multiply(value1, value2) { if (value1 === void 0) { value1 = 1; } if (value2 === void 0) { value2 = 1; } return value1 * value2; } console.log(multiply(4)); // 4