This is an interesting thing, which may also illustrate the power of Javascript objects. What we have to do is to output a Hello, World as mentioned in the previous article , and the input is print('Hello')('World'), and this is the so-called high-level function.
Higher-order functions
High-level seems like an esoteric term for an advanced programming technique, and I thought so when I first saw it.
Higher-order functions of Javascript
However, higher-order functions are just functions that take functions as parameters or return values. Take the above Hello, World as a simple example.
var Moqi = function(p1){
This.add = function (p2){
return p1 ' ' p2;
};
Return add;
};
We can use this function like this
console.log(Moqi('Hello')('World'));
Maybe this process is a bit confusing, so take a look at it in more detail.
> typeof Moqi('Hello')
<- "function"
> Moqi('Hello')
<- function (p2){
return p1 ' ' p2;
}
In other words, Moqi('Hello') is actually a function, Moqi('Hello')
> var m = Moqi('Hello')
> m('World')
> "Hello,World"
From the above situation, higher-order functions can make the code more concise and efficient. Naturally we can also create a function so that:
> Moqi('Hello')('World')('Phodal')
> "Hello,World Phodal"
So there is such a function
var Moqi = function(p1){
Return function (p2){
return function(p3){
return p1 ',' p2 ' ' p3;
}
};
};
Restore higher-order functions
It is becoming more and more complex, and the signal that higher-order function abstraction needs to be introduced is the occurrence of repeated or similar code. Then, we restore to the previous function step by step:
var Moqi = function(p1){
This.add = function (p2){
return function(p3){
return p1 ',' p2 ' ' p3;
}
};
Return this.add;
};
Then create a new function
Copy code The code is as follows:
var Moqi = function(p1){
This.add = function (p2){
This.add1 = function(p3){
return p1 ',' p2 ' ' p3;
};
return this.add1;
};
Return this.add;
};
Using the call method in javascript, there will be:
var Moqi = function(p1){
var self = this;
function fd(p2) {
This.add1 = function (p3) {
return p1 ',' p2 ' ' p3;
};
}
self.add = function (p2){
fd.call(this, p2);
return this.add1;
};
Return self.add;
};
Higher-order function examples
The above example is just for fun, the following example is for real application.
add = function(a,b){
Return a b;
};
function math(func,array){
Return func(array[0],array[1]);
}
console.log(math(add,[1,2]));
> math(add,[1,2])
< 3
In the above example, the add passed in is a parameter, and when returned, it is just a function. For example, there is a function in jQuery for
// Convert dashed to camelCase; used by the css and data modules
// Microsoft forgot to hump their vendor prefix (#9572)
camelCase: function( string ) {
Return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
},
It is also used in this way, which shows how important high-order functions are to mastering JS well. .
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