ES6 custom bind

es6-custom-bind.js

const bind = (target, context, ...bindedArgs) =>
  (...args) => target.call(context, ...bindedArgs, ...args);

// Example 1.
const sumFn = function(...args) {
  return [...args].reduce((prev, next) => prev + next, this.value);
};
const bindedSum = bind(sumFn, {value: 10}, 20, 30);
console.log(bindedSum(40, 50, 60)); // 210

// Example 2.
const list = (...args) => [...args];
const leadingThirtysevenList = bind(list, undefined, 37);
console.log(leadingThirtysevenList()); // [37]
console.log(leadingThirtysevenList(1, 2, 3)); // [37, 1, 2, 3]