Tips and Tricks(小技巧)

console(控制台)

运行多行的命令

Shift + Enter 允许您在控制台输入多行。

启动元素审查的快捷方式

Ctrl + Shift + C 或 Cmd + Shift + C 将快速启动 DevTools 检查元素的模式。

支持 console.table 命令

使用如下：

console.table([{a:1, b:2, c:3}, {a:"foo", b:false, c:undefined}]);
console.table([[1,2,3], [2,3,4]]);

还有一个可选的 columns 参数来选择需要输出的列。
如下：

function Person(firstName, lastName, age) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.age = age;
}

var family = {};
family.mother = new Person("Susan", "Doyle", 32);
family.father = new Person("John", "Doyle", 33);
family.daughter = new Person("Lily", "Doyle", 5);
family.son = new Person("Mike", "Doyle", 8);

console.table(family, ["firstName", "lastName", "age"]);

如果只想输出出前两列，可以：

console.table(family, ["firstName", "lastName"]);

预览在控制台打印出的对象

可以直接使用console.log()预览打印出的对象，不需要做额外的工作。

传递多个参数控制打印日志的样式

你可以通过 %c 将样式添加到您的控制台日志,就像你可以在Firebug中做的一样。如：

console.log('%cBlue! %cRed!', 'color: blue;', 'color: red;');

清空控制台历史的快捷键

做一个键盘侠

从控制台快速的选择元素

Select an element and type $0 in the console, it will be used by the script. If you have jQuery on the page, you can then use $($0) to reselect the element in the page.

You can also right click on any element output to the console and click 'Reveal in Elements Panel' to find it in the DOM.

用XPath表达式选择DOM

XPath is a query language for selecting nodes from documents and generally returns a node-set, string, boolean or number. You can use XPath expressions to query the DOM from the DevTools JavaScript console.

The $x(xpath) command will allow you to execute a query - see below for an example of how to search for the images in a page using $x('//img'):

However, the function also accepts an optional second argument for the path context - i.e $x(xpath, context). This lets us select a specific context (e.g an iframe) and run an XPath query against it.

var frame = document.getElementsByTagName('iframe')[0].contentWindow.document.body;
$x('//'img, frame);

which queries the images within the specified iframe.

得到控制台最后一个输出的结果

使用 $_ 得到控制台最后一个输出的结果.

console.dir()

在指定的 iframe 中运行控制台中命令

Along the bottom bar of the DevTools are drop-down options that change depending on the context of your current tab. When you’re in the Console panel, there’s a drop-down that allows you to select the frame context that the console will operate in. Select your frame in the drop-down and you’ll find yourself in the right context in no time.

当浏览器切换到另一个页面时保存控制台中历史

在控制台版面右键，选择 save 即可

console.time() 和 console.timeEnd()

可以 console.time() 和 console.timeEnd() 计算程序运行的时间.如下：

console.profile() 和 console.profileEnd()

DevTools打开时,调用 console.profile() JavaScript CPU的分析。console.profileEnd() 结束此次分析。如下：

每次分析都被加到 Profiles面板和 `console.profilses'中:

Elements

打开尺标线

打开 Devtools Settings > General > Show rulers即可

css 属性的自动补全

颜色选择器

在Devtools中点击颜色时可以调出一个颜色选择器。用 shift + 'click' 可以改变颜色的样式。

新增CSS 样式

在Elements面板中拖曳元素

在Elements中拖曳元素可以改变该元素在文档流中的未知和显示的样式。

改变元素的状态

• Right click on a child element and select 'Inspect Element'
• In the Elements panel right-click the parent element and choose "Force Element State"
• You can now choose one of :active, :hover, :focus or :visited to force the element into one of these states.

调试 less 或者 sass 代码

Settings > General > Sources > Enable CSS source maps

Timeline