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JavaScript Patterns 5.4 Module Pattern

2024-07-09 16:31:03   223人阅读

MYAPP.namespace(‘MYAPP.utilities.array‘);MYAPP.utilities.array = (function () {    // dependencies    var uobj = MYAPP.utilities.object,        ulang = MYAPP.utilities.lang,        // private properties        array_string = "[object Array]",        ops = Object.prototype.toString;    // private methods    // ...    // end var    // optionally one-time init procedures    // ...    // public API    return {        inArray: function (needle, haystack) {            for (var i = 0, max = haystack.length; i < max; i += 1) {                if (haystack[i] === needle) {                    return true;                }            }        },        isArray: function (a) {            return ops.call(a) === array_string;        }        // ... more methods and properties    };}());

Revealing Module Pattern

Privacy pattern

The above can become:

MYAPP.utilities.array = (function () {    // private properties    var array_string = "[object Array]",        ops = Object.prototype.toString,        // private methods        inArray = function (haystack, needle) {            for (var i = 0, max = haystack.length; i < max; i += 1) {                if (haystack[i] === needle) {                    return i;                }            }            return−1;        },        isArray = function (a) {            return ops.call(a) === array_string;        };    // end var    // revealing public API    return {        isArray: isArray,        indexOf: inArray    };}()); 

Modules That Create Constructors

The only difference is that the immediate function that wraps the module will return a function at the end, and not an object.

MYAPP.namespace(‘MYAPP.utilities.Array‘);MYAPP.utilities.Array = (function () {    // dependencies    var uobj = MYAPP.utilities.object,        ulang = MYAPP.utilities.lang,        // private properties and methods...        Constr;    // end var    // optionally one-time init procedures    // ...    // public API -- constructor    Constr = function (o) {        this.elements = this.toArray(o);    };    // public API -- prototype    Constr.prototype = {        constructor: MYAPP.utilities.Array,        version: "2.0",        toArray: function (obj) {            for (var i = 0, a = [], len = obj.length; i < len; i += 1) {                a[i] = obj[i];            }            return a;        }    };    // return the constructor    // to be assigned to the new namespace    return Constr;}());var arr = new MYAPP.utilities.Array(obj);

Importing Globals into a Module

In a common variation of the pattern, you can pass arguments to the immediate function that wraps the module. You can pass any values, but usually these are references to global variables and even the global object itself. Importing globals helps speed up the global symbol resolution inside the immediate function, because the imported variables become locals for the function.

MYAPP.utilities.module = (function (app, global) {    // references to the global object    // and to the global app namespace object    // are now localized}(MYAPP, this));

 

References: 

JavaScript Patterns - by Stoyan Stefanov (O`Reilly)


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