//js 文件

var canvas = {

    ctx: null,

    createCtx: function () {

    this.ctx = wx.createCanvasContext('tab_canvas')

    },

    initCanvas: function (point, widht, showItem) {

        console.log("initCanvas", this.ctx)

         if (!this.ctx) {

            this.createCtx();

           }

            ...

  ｝

｝

module.exports = canvas

//pages 文件

var canvas = require('../../../utils/canvas2.js')

Page({

onLoad: function (options) {

    ... 

    canvas.initCanvas(array, that.data.canvasW)

｝

})

-----------------------------------END--------------------------------

 console.log("initCanvas", this.ctx)

这句日志的输出 第一次进入页面 为null 退出页面 再进去后竟然有值了