201506250923_ JavaScript authoritative Guide (sixth edition)-checking for functions, incomplete functions, memory functions (P193-200)

One. Check whether it is a function.

function Isfunction (x) {

return Object.prototype.toString.call (x) = = = "[Object Function]";

};

function square (n) {

return n*n;

};

Alert (isfunction (square)); true

I. Functional programming

1. Working with arrays using functions

For example:

function fn () {//some code ...}; Elemnets.reduce (FN);

2. Higher-order functions--functions of operation functions

For example:

Function not (f) {

return function () {

var result = f.apply (this,arguments);

Return!result

}

};

var even = function (x) {return x%2 = = = 0};

var odd = not (even);

Alert ([1,1,3,5,7,9].every (odd)); //true to determine if it is an odd number

3. Incomplete functions

4. Memory

For example:

A function with memory capability

function memorize (f) {

var cache = {};

return function () {

var key = Arguments.length + Array.prototype.join.call (arguments, ",");

if (key in cache) return Cache[key];

else return Cache[key] = f.apply (this,arguments);

};

};

Greatest common divisor algorithm functions

function Zdgys (A, b) {

var T; if (a < b) {

t = B,b = A, a = t;

};

while (b! = 0) {

t = B,b = a%b, a = t;

};

return A;

};

var instance = memorize (Zdgys);

Alert (instance (27,54)); -

5.

201506250923_ JavaScript authoritative Guide (sixth edition)-checking for functions, incomplete functions, memory functions (P193-200)