微信小程序开发实战——使用Underscore.js

摘要：是一个工具库，它提供了一整套函数式编程的实用功能，但是没有扩展任何内置对象。微信小程序无法直接使用进行调用。通过测试，微信小程序运行环境并没有定义获取应用实例解决方法修改代码，注释原有模块导出语句，使用强制导出使用获取应用实例其他完整代码

Underscore.js 是一个 JavaScript 工具库，它提供了一整套函数式编程的实用功能，但是没有扩展任何 JavaScript 内置对象。Underscore 提供了100多个函数，包括常用的：map、filter、invoke — 当然还有更多专业的辅助函数，如：函数绑定、JavaScript 模板功能、创建快速索引、强类型相等测试等等。 微信小程序无法直接使用require( "underscore.js" )进行调用。

微信小程序运行环境支持CommoJS模块化，通过module.exports暴露对象，通过require来获取对象。

微信小程序Quick Start utils/util.js

function formatTime(date) {
  var year = date.getFullYear()
  var month = date.getMonth() + 1
  var day = date.getDate()

  var hour = date.getHours()
  var minute = date.getMinutes()
  var second = date.getSeconds();


  return [year, month, day].map(formatNumber).join("/") + " " + [hour, minute, second].map(formatNumber).join(":")
}

function formatNumber(n) {
  n = n.toString()
  return n[1] ? n : "0" + n
}

module.exports = {
  formatTime: formatTime
}

pages/log/log.js

var util = require("../../utils/util.js")
Page({
  data: {
    logs: []
  },
  onLoad: function () {
    this.setData({
      logs: (wx.getStorageSync("logs") || []).map(function (log) {
        return util.formatTime(new Date(log))
      })
    })
  }
})

Underscore CommonJs模块导出代码如下：

// Export the Underscore object for **Node.js**, with
// backwards-compatibility for the old `require()` API. If we"re in
// the browser, add `_` as a global object.
if (typeof exports !== "undefined") {
  if (typeof module !== "undefined" && module.exports) {
     exports = module.exports = _;
  }
  exports._ = _;
} else {
  root._ = _;
}

exports、module必须都有定义，才能导出。通过测试，微信小程序运行环境exports、module并没有定义

//index.js

//获取应用实例
var app = getApp();

Page({ 

  onLoad: function () {
    console.log("onLoad");
    var that = this;

    console.log("typeof exports: " + typeof exports);    
    console.log("typeof module: " + typeof exports); 

    var MyClass = function() {

    }

    module.exports = MyClass;

    console.log("typeof module.exports: " + typeof module.exports);   
  }
})

修改Underscore代码，注释原有模块导出语句，使用module.exports = _ 强制导出

    /*
    // Export the Underscore object for **Node.js**, with
    // backwards-compatibility for the old `require()` API. If we"re in
    // the browser, add `_` as a global object.
    if (typeof exports !== "undefined") {
      if (typeof module !== "undefined" && module.exports) {
        exports = module.exports = _;
      }
      exports._ = _;
    } else {
      root._ = _;
    }
    */

    module.exports = _;

    /*
    // AMD registration happens at the end for compatibility with AMD loaders
    // that may not enforce next-turn semantics on modules. Even though general
    // practice for AMD registration is to be anonymous, underscore registers
    // as a named module because, like jQuery, it is a base library that is
    // popular enough to be bundled in a third party lib, but not be part of
    // an AMD load request. Those cases could generate an error when an
    // anonymous define() is called outside of a loader request.
    if (typeof define === "function" && define.amd) {
      define("underscore", [], function() {
        return _;
      });
    }
    */

//index.js

var _ = require( "../../libs/underscore/underscore.modified.js" );

//获取应用实例
var app = getApp();


Page( {

    onLoad: function() {
        //console.log("onLoad");
        var that = this;

        var lines = [];

        lines.push( "_.map([1, 2, 3], function(num){ return num * 3; });" );
        lines.push( _.map( [ 1, 2, 3 ], function( num ) { return num * 3; }) );

        lines.push( "var sum = _.reduce([1, 2, 3], function(memo, num){ return memo + num; }, 0);" );
        lines.push( _.reduce( [ 1, 2, 3 ], function( memo, num ) { return memo + num; }, 0 ) );

        lines.push( "var even = _.find([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });" );
        lines.push( _.find( [ 1, 2, 3, 4, 5, 6 ], function( num ) { return num % 2 == 0; }) );

        lines.push( "_.sortBy([1, 2, 3, 4, 5, 6], function(num){ return Math.sin(num); });" );
        lines.push( _.sortBy( [ 1, 2, 3, 4, 5, 6 ], function( num ) { return Math.sin( num ); }) );

        lines.push( "_.indexOf([1, 2, 3], 2);" );
        lines.push( _.indexOf([1, 2, 3], 2) );

        this.setData( {
            text: lines.join( "
" )
        })
    }
})

完整代码 https://github.com/guyoung/Gy...