Detailed explanation of JavaScript function currying
What is currying
Currying is a conversion process that transforms a function that accepts multiple parameters Becomes a function that accepts a single parameter (Annotation: the first parameter of the original function). If other parameters are necessary, returns a new function that accepts the remaining parameters and returns the result.
Ke Lihua function idea: a js pre-processing idea; the principle of using function execution to form a scope that is not destroyed, Store all the content that needs to be pre-processed in this scope that is not destroyed, and return a small function. From now on, we will execute small functions. In the small function, we can perform relevant operations on the previously stored values;
The currying function mainly plays the role of preprocessing;
The role of the bind method: Pass in This in the callback method is pre-processed as context;
bind method implementation principle 1 The code is as follows:
/**
* bind方法实现原理1
* @param callback [Function] 回调函数
* @param context [Object] 上下文
* @returns {Function} 改变this指向的函数
*/
function bind(callback,context) {
var outerArg = Array.prototype.slice.call(arguments,2);
// 表示取当前作用域中传的参数中除了fn,context以外后面的参数；
return function (){
var innerArg = Array.prototype.slice.call(arguments,0);//表示取当前作用域中所有的arguments参数；
callback.apply(context,outerArg.concat(innerArg));
}
}The following piece of code imitates the binding implementation principle on the prototype chain
/**
* 模仿在原型链上的bind实现原理(柯理化函数思想)
* @param context [Object] 上下文
* @returns {Function} 改变this指向的函数
*/
Function.prototype.mybind = function mybind (context) {
var _this = this;
var outArg = Array.prototype.slice.call(arguments,1);
// 兼容情况下
if('bind' in Function.prototype) {
return this.bind.apply(this,[context].concat(outArg));
}
// 不兼容情况下
return function () {
var inArg = Array.prototype.slice.call(arguments,0);
inArg.length === 0?inArg[inArg.length]=window.event:null;
var arg = outArg.concat(inArg);
_this.apply(context,arg);
}
}Function currying (Currying)
in In computer science, currying is a technique that transforms a function that accepts multiple parameters into a function that accepts a single parameter (the first parameter of the original function), and returns a new function that accepts the remaining parameters and returns a result
Currying is to pass in certain parameters in advance to get a simple function. But the parameters passed in beforehand are saved in the closure, so there will be some peculiar characteristics. For example:
Example:
var adder = function(num) {
return function(y) {
return num + y;
}
}
var inc = adder(1);
var dec = adder(-1);
//inc, dec现在是两个新的函数，作用是将传入的参数值（+/-）1
alert(inc(99));//100
alert(dec(101));//100
alert(adder(100)(2));//102
alert(adder(2)(100));//102 The above is the detailed explanation of JavaScript function currying. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!
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