In this example, we have a string with only one comma. The regular expression/^(.+?),/matches and captures everything before the first comma. By referring to the captured group as$1in the replacement string, we keep it as is and effectively remove only the first comma. Conclusion Removi...
number – 如果变量是 Number 类型的 string – 如果变量是 String 类型的 object – 如果变量是一种引用类型或 Null 类型的 3)通过instanceof 运算符解决引用类型判断问题 4)null 被认为是对象的占位符,typeof运算符对于null值返回“object”。 5)原始数据类型和引用数据类型变量在内存中的存放如下: 6)JS中对...
lastName){ greetingMsg = greetingMsg + firstName + " " + lastName; } return { sendGreeting: function(firstName, lastName){ msgTo(firstName, lastName); } getMsg: function(){ return greetingMsg; } } } const createMsg = sayHello(); createMsg.send...
ECMAScript 中有 5 种简单数据类型(也称为基本数据类型):Undefined、Null、Boolean、Number和 String。还有 1 种复杂数据类型——Object,Object 本质上是由一组无序的名值对组成的。 typeof操作符 鉴于ECMAScript 是松散类型的,因此需要有一种手段来检测给定变量的数据类型——typeof 就 是负责提供这方面信息的操...
range.setStart(textNode, 0); // Start at first character range.setEnd(textNode, 5); // End at fifth character document.getElementById("log").textContent = range; 3.16. setEnd() setEnd(endNode, endOffset):设置终点。 const range = document.createRange(); ...
19.1 Use soft tabs (space character) set to 2 spaces. eslint: indent // bad function foo() { ∙∙∙∙let name; } // bad function bar() { ∙let name; } // good function baz() { ∙∙let name; }19.2 Place 1 space before the leading brace. eslint: space-before-...
range.moveEnd("character",input.value.length); range.select(); 演示如下: 切记:使用F5刷新没有用的,要在地址栏中,然后按enter键刷新即可看到效果; //选择前3个字符range.collapse(true); range.moveStart("character",0); range.moveEnd("character",3); ...
side_effects (default: true)— drop extraneous code which does not affect outcome of runtime execution. spreads (default: true)— flatten spread expressions. strings (default: true)— compact string concatenations. switches (default: true)— de-duplicate and remove unreachable switch branches templa...
9. Swap Case in String Write a JavaScript program that accepts a string as input and swaps the case of each character. For example if you input 'The Quick Brown Fox' the output should be 'tHE qUICK bROWN fOX'. Click me to see the solution ...
String indexes refer to using numerical characters to obtain a single character in a string. For example, in the string “abc”, you can refer to the letter a by using a string index of zero (e.g. “abc”[0]). Making a number from a string is pretty easy in JavaScript. You need...