SOURCE

Function.prototype.myapply = function (context, args) {
	context = context || window
	context.fn = this
	let result
	if (!args) {
		result = context.fn()
	} else {
		let temp = []
		for (let i = 0, len = args.length; i < len; i++) {
			temp.push('args[' + i + ']')
		}
		result = eval('context.fn(' + temp + ')')
	}
	
	delete context.fn
	return result
}