bind.js

Function.prototype.bind1 = function (scope) {
  let fn = this
  let prefixArgs = Array.prototype.slice.call(arguments, 1)
  
  return function() {
    let suffixArgs = Array.prototype.slice.call(arguments)
    let args = prefixArgs.concat(suffixArgs)
    return fn.apply(scope, args)
  } 
}

// Ex 1: Create a function with a preset leading argument
function list() {
  // arguments is an array-like object. convert arguments to an array.  
  return Array.prototype.slice.call(arguments);
}
console.log( list(1, 2, 3) ) // [1, 2, 3]

var leadingThirtysevenList = list.bind1(null, 37)
console.log( leadingThirtysevenList() ) // [37]
console.log( leadingThirtysevenList(1, 2, 3) ) // [37, 1, 2, 3]

// Ex 2: Changing the scope of `this`
var foo = {
  x: 3
}

function bar (){
  console.log(this.x)
}

var boundFunc = bar.bind1(foo)
boundFunc() // 3