1.startsWith方法在MWD中的实现: if (!String.prototype.startsWith) { Object.defineProperty(String.prototype, 'startsWith', { value: function(search, pos) { pos = !pos || pos < 0 ? 0 : +pos; return this.substring(pos,
① startsWidth: if(typeofString.prototype.startsWith != 'function') {//在引用类型的原型链上添加这个方法,只需要添加一次,因此进行判断String.prototype.startsWith =function(prefix){returnthis.slice(0, prefix.length) ===prefix; }; } ② endsWith: 1if(typeofString.prototype.endsWith != 'function...
if(typeofString.prototype.startsWith !='function') { String.prototype.startsWith =function(prefix){ returnthis.slice(0, prefix.length) === prefix; }; } String.slice()和String.substring()类似,都是获得一段子串,但有评测说slice的效率更高。这里不使用indexOf()的原因是,indexOf会扫描整个字符串,...
We can call the regex test method on the following expression\^\s*$\and pass on the string to detect if the string starts with a white space or not in JavaScript. Example functionstartsWithSpace(str){return/^\s/.test(str); }console.log(startsWithSpace(' hello'))// trueconsole.log(...
Returns true if the string starts with the value, otherwise it returns false JavaScript Version: ECMAScript 6More ExamplesCheck if a string starts with "world", starting the search at position 6: var str = "Hello world, welcome to the universe."; var n = str.startsWith("world", 6); ...
text.startsWith("Hello"); Try it Yourself » Start at position 1 (false): lettext ="Hello world, welcome to the universe."; text.startsWith("Hello",1); Try it Yourself » Description ThestartsWith()method returnstrueif a string starts with a specified string. ...
Example 1: Using endsWith() Method // string definitionletsentence ="JavaScript is fun"; // checking if the given string ends with "fun"letcheck = sentence.endsWith("fun"); console.log(check); // checking if the given string ends with "is"letcheck1 = sentence.endsWith("is"); ...
The startsWith() method returns true if a string begins with specified character(s). If not, it returns false. Example const message = "JavaScript is fun"; // check if message starts with Java let result = message.startsWith("Java"); console.log(result); // true // check if ...
if ( name[0] === "d" && name[1] === "a" && name[2] === "t" && name[3] === "a" && name[4] === "-" ) { // ... } if ( sel[0] === "s" && sel[1] === "v" && sel[2] === "g" && (sel.length === 3 || sel[3] === "." || sel[3] ===...
If you ever need to check if a string begins with another string in JavaScript, use ES6's startsWith method...