markdown JS：Bind，Call，Apply

Posted 2021-05-05

## Function calls: call, apply and bind
All of these three methods are used to attach this into function and the difference is in the function invocation.

**.call()** invokes the function immediately and requires you to pass in arguments as a list (one by one).

**.apply()** invokes the function immediately and allows you to pass in arguments as an array.

**.call()** and .apply() are mostly equivalent and are used to borrow a method from an object. Choosing which one to use depends on which one is easier to pass the arguments in. Just decide whether it’s easier to pass in an array or a comma separated list of arguments.

### Quick tip: Apply for Array — Call for Comma.
```sh
const Snow = {surename: 'Snow'}

const char = {
  surename: 'Stark',
  knows: function(arg, name) {
    console.log(`You know ${arg}, ${name} ${this.surename}`);
  }
}

char.knows('something', 'Bran');              // You know something, Bran Stark
char.knows.call(Snow, 'nothing', 'Jon');      // You know nothing, Jon Snow
char.knows.apply(Snow, ['nothing', 'Jon']);   // You know nothing, Jon Snow
```