JavaScript Console 之浏览器控制台
Chrome 几乎是最好的浏览器，是的，我一直这么认为，它的开发者工具也觉不含糊，来，试一试 Console。
输出信息
输出日志信息
// 普通日志信息console.log('this is a log');// 简单样式的日志信息var template = '%cHello World!', style = 'font-size: 30px; color: blue;';console.log(template, style);// 华丽样式的日志信息var template = '%cHello World!', style = '';style += 'background-image: -webkit-gradient(linear, left top, right top,';style += 'color-stop(0, #f22), color-stop(0.15, #f2f), color-stop(0.3, #22f),';style += 'color-stop(0.45, #2ff), color-stop(0.6, #2f2),color-stop(0.75, #2f2),';style += 'color-stop(0.9, #ff2), color-stop(1, #f22));';style += 'color: transparent; -webkit-background-clip: text; font-size: 6em;)';console.log(template, style);// 图片日志信息var style = 'padding: 150px 200px; line-height: 300px; background: url(http://www.wyzu.cn/data/uploadfile/200803/2008032812262650.gif) no-repeat;';console.log('%c', style);// 接受不定参数console.log('%cHello World!', 'color: red;', 'JavaScript', 'Web Developer');
输出提示信息
console.info('this is a info');输出警告信息
console.warn('this is a warn.');输出错误信息
console.error('this is a error');输出分组信息
// 普通组console.group('App.log');console.log('this is a group log.');console.groupEnd();console.group('App.info');console.info('this is a group info.');console.groupEnd();// 组嵌套var user = 'Atkinson', authenticated = true, authorized = true;console.group("Authenticating user '%s'", user);if (authenticated) {console.log("User '%s' was authenticated.", user);console.group("Authorizing user '%s'.", user);if (authorized) {console.log("User '%s' was authorized.", user);}console.groupEnd();}console.groupEnd();console.log("A nested group log trace.");// 折叠组var user = 'Atkinson', authenticated = true, authorized = true;console.groupCollapsed("Authenticating user '%s'", user);if (authenticated) {console.log("User '%s' was authenticated.", user);console.groupCollapsed("Authorizing user '%s'.", user);if (authorized) {console.log("User '%s' was authorized.", user);}console.groupEnd();}console.groupEnd();console.log("A nested group log trace.");
字符串替换和格式
格式说明符的完整列表
console.log("Node count: %d, and the time is %f.", document.childNodes.length, Date.now());将 DOM 结点以 JavaScript 对象的形式输出到控制台
console.dir(document.body);console.dir(document.body.firstElementChild);
输出表格信息
// 基本表格var table = [{'名称': 'MacBook Pro', '数量': 2, '单位': '台'},{'名称': 'ThinkPad', '数量': 10, '单位': '台'},{'名称': 'JavaScript 工程师', '数量': 2, '单位': '人'},{'名称': 'PHP 工程师', '数量': 10, '单位': '人'}];console.table(table);// 高级表格function Person(name, email, age) {this.name = name;this.email = email;this.age = age;}var language = {};language.c = new Person('C', 'clang@gmail.com', 40);language.php = new Person('PHP', 'php@gmail.com', 25);language.java = new Person('Java', 'java@gmail.com', 30)language.javascript = new Person('JavaScript', 'javascript@gmail.com', 20);console.table(language, ['name', 'email', 'age']);
断言
// 代替三目运算，先对传入的表达式进行断言，只有表达式为假时才输出信息var isDebug = false;console.log(isDebug, '请稍候, 系统正在调试中...');
堆栈跟踪
function add(num) {if (num > 0) {console.trace('recursion is function:', num);return num + add(num - 1);} else {return 0;}}add(3);
计数
// 统计某段代码执行了多少次var Test = function() {var testFunc = function() {console.count('`testFunc()` 函数被执行的次数');};return {init: function() {testFunc();}};};var f = new Test();f.init(); // `testFunc()` 函数被执行的次数：1f.init(); // `testFunc()` 函数被执行的次数：2
统计任务耗时
console.time('Array initialize');var array = new Array(1000000);for (var i = array.length - 1; i >= 0; i--) {array[i] = new Object();}console.timeEnd('Array initialize'); // Array initialize: 1416.217ms
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