30秒学会 JavaScript 片段 – bind

Creates a function that invokes fn with a given context, optionally adding any additional supplied parameters to the beginning of the arguments.

Return a function that uses Function.prototype.apply() to apply the given context to fn.
Use Array.prototype.concat() to prepend any additional supplied parameters to the arguments.

代码片段

const bind = (fn, context, ...boundArgs) => (...args) => fn.apply(context, [...boundArgs, ...args]);

使用样例

function greet(greeting, punctuation) {
  return greeting + ' ' + this.user + punctuation;
}
const freddy = { user: 'fred' };
const freddyBound = bind(greet, freddy);
console.log(freddyBound('hi', '!')); // 'hi fred!'