兼容版本

var slice = Array.prototype.slice;
function bind(asThis){
    var args = slice.call(arguments,1);
    var fn = this;
    return function(){
        var agrs2 = slice.call(arguments,0);
        return fn.apply(asThis,args.concat(agrs2))
    }
}
module.exports =  bind;

if(! Function.prototype.bind){
    Function.prototype.bind = bind;
}

ES6版本

function bind(asThis,...args){
    const fn = this;
    return function(...args2){
        return fn.call(asThis,...args,...args2)
    }
}
module.exporte = bind;
if(!Function.prototype.bind){
       Function.prototype.bind = bind
}