Call function with array of arguments

by

Since the introduction of ES6, you can sue the spread syntax in the function call:

const args = [1,2,3];

fn(...args);

function fn() {
  console.log(arguments);
}

Before ES6, you needed to use apply.

var args = [1,2,3];
fn.apply(null, args);

function fn() {
  console.log(arguments);
}

Both will produce the equivalent function call:

fn(1,2,3);

Notice that I used null as the first argument of the apply example, which will set the this keyword to the global object (window) inside fn or undefined under strict mode.

Also, you should know that the arguments object is not an array, it’s an array-like object, that contains numeric indexes corresponding to the arguments that were used to call your function, a length property that gives you the number of arguments used.

In ES6, if you want to access a variable number of arguments as an array, you can also use the rest syntax in the function parameter list:

function fn(...args) {
  args.forEach(arg => console.log(arg))
}

fn(1,2,3)

Before ES6, if you wanted to make an array from your arguments object, you commonly used the Array.prototype.slice method.

function fn() {
  var args = Array.prototype.slice.call(arguments);
  console.log(args);
}

fn(1,2,3);

Edit: In response to your comment, yes, you could use the shift method and set its returned value as the context (the this keyword) on your function:

fn.apply(args.shift(), args);

But remember that shift will remove the first element from the original array, and your function will be called without that first argument.

If you still need to call your function with all your other arguments, you can:

fn.apply(args[0], args);

And if you don’t want to change the context, you could extract the first argument inside your function:

function fn(firstArg, ...args) {
   console.log(args, firstArg);
}

fn(1, 2, 3, 4)

In ES5, that would be a little more verbose.

function fn() {
  var args = Array.prototype.slice.call(arguments),
        firstArg = args.shift();

  console.log(args, firstArg);
}

fn(1, 2, 3, 4);

More Related Contents:

  1. What is “undefined x 1” in JavaScript?
  2. How can I convert the “arguments” object to an array in JavaScript?
  3. Converting an array to a function arguments list [duplicate]
  4. Why is this javascript Array() producing an array with only one element? [closed]
  5. adding array elements with for loop JavaScript
  6. Sum similar keys in an array of objects
  7. Best way to iterate over an array without blocking the UI
  8. How to compute the sum and average of elements in an array?
  9. Copy array items into another array
  10. Uploading multiple files using formData()
  11. Find and remove objects in an array based on a key value in JavaScript
  12. JavaScript – populate drop down list with array
  13. Explanation of [].slice.call in javascript?
  14. How to filter an array in javascript?
  15. Get unique results from JSON array using jQuery
  16. Compare 2 arrays which returns difference
  17. Getting a list of associative array keys
  18. How to find duplicate values in a JavaScript array of objects, and output only unique values?
  19. How much faster are arrays than accessing Google Sheets cells within Google Scripts?
  20. Getting index of an array’s element based on its properties
  21. Push Object in Array [duplicate]
  22. Javascript array sort and unique
  23. How to sort array of objects based on a boolean property?
  24. Can I append an array to ‘formdata’ in javascript?
  25. Finding all permutations of array elements as concatenated strings
  26. Array.map doesn’t seem to work on uninitialized arrays [duplicate]
  27. Node.js – console.log does not show items in array but instead shows [Object]
  28. A better way to splice an array into an array in javascript
  29. Create a dynamic nested object from array of properties
  30. Javascript: Sort array of arrays by second element in each inner array

Leave a Comment