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Setting default arguments with JavaScript arrow functions

Yesterday, we looked at how to set default values for JavaScript function arguments.

With arrow functions, it’s even easier.

You can set a default value for each argument at the time that you give it a name with = value.

// Setting defaults with a traditional function
var add = function (num1, num2) {

	// If num1 or num2 aren't defined, set them to 0
	num1 = num1 || 0; // conditional operator
	num2 = num2 ? num2 : 0; // ternary operator

	// Add the numbers
	return num1 + num2;


// Setting defaults with an arrow function
var add = (num1 = 0, num2 = 0) => num1 + num2;

Arrow functions aren’t production-ready at the moment—they require a compiler to have good enough browser compatibility—but this is still a great feature.

If you like this post, you might also enjoy my vanilla JS pocket guide on variables, functions, and scope.