可以使用String作为toString()更可靠的代替方法,因为它在用于null和undefined时仍然有效。例如: js constnullVar=null;nullVar.toString();// TypeError: nullVar is nullString(nullVar);// "null"constundefinedVar=undefined;undefinedVar.toString();// TypeError: undefinedVar is undefinedString(undefinedVar);/...
jsCopy to Clipboard const text = "Mozilla"; console.log(text.substring(5, 2)); // "zil" console.log(text.slice(5, 2)); // "" 如果两个参数中的任何一个或两个都是负数或 NaN,substring() 方法将把它们视为 0。 jsCopy to Clipboard console.log(text.substring(-5, 2)); // "Mo"...
If you're just checking for one singular character, you can try this. But note when you have more than character (ie. hel), this method won't work. constword='hello';word[0]==='h'; Thanks:@neutrino2211 #Performance Check @gwardwell:Here’s one such test (found on JSPerf, I did...
jsCopy to Clipboard concat(str1) concat(str1, str2) concat(str1, str2, /* …, */ strN) 参数 str1、……、strN 要连接到 str 的一个或多个字符串。尽管技术上允许,但不带参数地调用 String.prototype.concat() 毫无意义,因为它不会(像 Array.prototype.concat())返回可观察的拷贝——字符串...
@super.pro.dev:I also know: new String (foo) but I don't like this method (it will create an object of String, in contrast to String (without "new") which create string primitive) @BrunoGiubilei:when concat empty string, it's mostly correct to declare the empty strings first, becaus...
Different methods to check if string contains spaces in JavaScript Method-1: UseindexOfmethod Not to be confused with the arrayindexOfmethod, theString.prototype.indexOf()takes a string argument and searches for it within the string it’s called upon and returns the index of the first occurren...
TheRegExp.test()method returnstrueif the regular expression is matched in the string andfalseotherwise. The forward slashes/ /mark the beginning and end of the regular expression. index.js functionendsWithNumber(str){return/[0-9]+$/.test(str);} ...
Note that string is a primitive type in JavaScript, so strings are immutable.String.prototype.splicewill return the modified string, instead of modifying the original string, as opposed toArray.prototype.splice, which modifies the original array on which the method is called. ...
Sign in or create an account: GitHub Sign in: Persona Theslice()method extracts a section of a string and returns a new string. Syntax str.slice(beginSlice[,endSlice]) Parameters beginSlice The zero-based index at which to begin extraction. If negative, it is treated assourceLength + beg...
You know String.prototype.replace() in JavaScript? This method takes two parameters: pattern and replacement. Pattern is usually a string or regular expression. Technically it can be any object with a Symbol.replace method (like a RegExp). Replacement is either a string or function that returns...