1.在 utils 文件中新建 mcaptcha.js 文件，写入以下代码：

module.exports = class Mcaptcha { //画板 constructor(options) { this.options = options; this.fontSize = options.height * 3 / 4; this.init(); this.refresh(this.options.code); } init() { this.ctx = wx.createCanvasContext(this.options.el); this.ctx.setTextBaseline("middle"); this.ctx.setFillStyle(this.randomColor(180, 240)); this.ctx.fillRect(0, 0, this.options.width, this.options.height); } //绘制彩图 refresh(code) { let arr = (code + '').split(''); let width = this.options.width; let height = this.options.height; let ctx = this.ctx; if (arr.length === 0) { arr = ['e', 'r', 'r','o','r']; }; let offsetLeft = width * 0.6 / (arr.length - 1); let marginLeft = width * 0.2; arr.forEach((item, index) => { ctx.setFillStyle(this.randomColor(0, 180)); let size = this.randomNum(24, this.fontSize); ctx.setFontSize(size); let dis = offsetLeft * index + marginLeft - size * 0.3; let deg = this.randomNum(-30, 30); ctx.translate(dis, height*0.5); ctx.rotate(deg * Math.PI / 180); ctx.fillText(item, 0, 0); ctx.rotate(-deg * Math.PI / 180); ctx.translate(-dis, -height * 0.5); }) //绘制干扰线 for (var i = 0; i < 2; i++) { ctx.strokeStyle = this.randomColor(40, 180); ctx.beginPath(); ctx.moveTo(this.randomNum(0, width), this.randomNum(0, height)); ctx.lineTo(this.randomNum(20, width), this.randomNum(2, height)); ctx.stroke(); } //绘制干扰点 for (var i = 0; i < 30; i++) { ctx.fillStyle = this.randomColor(0, 255); ctx.beginPath(); ctx.arc(this.randomNum(0, width), this.randomNum(0, height), 1, 0, 2 * Math.PI); ctx.fill(); } ctx.draw(); } //设置随机数的颜色 randomNum(min, max) { return Math.floor(Math.random() * (max - min) + min); } randomColor(min, max) { let r = this.randomNum(min, max); let g = this.randomNum(min, max); let b = this.randomNum(min, max); return "rgb(" + r + "," + g + "," + b + ")"; }}

2.在需要验证码的js文件中引入

let Mcaptcha = require("../../../utils/mcaptcha.js");

res.data 是要传到mcaptcha.js 中的 code 值，也就是验证码，可以随意写为如：“ho55”，“a2sd” 等等。我这里是从后台传过来的数据，（前人写的代码，不好改动，只在前端加上干扰线和彩图）。

new Mcaptcha({ el: 'canvas', width: 100, height: 30, code: res.data});

wxml 文件， bindtap="getImgYZM" 是 new Mcaptcha 的方法名，再次点击可以换验证码图片。

<view bindtap="getImgYZM" class="yzm"> <canvas style="width:{{cvs.width}};height:{{cvs.height}};" canvas-id="canvas"></canvas></view>

如果是在前端设置随机数，可以在data:{} 里面写

data: { str:"0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z", randStr:"" }//获取随机数var res = "";for(var i = 0; i < str.length ; i ++) { var id = Math.ceil(Math.random()*35); res += chars[id];}return res;

这一步可不看，以下是后端C#语言产生随机数返给前端的代码：

using JobClass;using System;using System.Collections.Generic;using System.Drawing;using System.Linq;using System.Web;using System.Web.SessionState;namespace WebSite.pcode{ /// <summary> /// getcode 的摘要说明 /// </summary> public class getcode : IHttpHandler, IRequiresSessionState { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; string str = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z"; string randStr = ""; //生成随机数 Random Random randobj = new Random(); string[] arr = str.Split(','); for (int i = 0; i < 4; i++) { randStr += arr[randobj.Next(arr.Length)]; } context.Response.Write(randStr); return; } public bool IsReusable { get { return false; } } }}

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