To check if a Javascript String Contains a substring or not, we can use 7 different Javascript methods as listed in below table.
In JavaScript, we can use the classic indexOf() or the new ES6 includes to check if a String contains a substring. // old school, classic way var str ="mkyong"; if(str.indexOf('yo') > -1) {// returns `-1` if it is not present. console.log('match')// display this }else{...
As a more complex example, let's say you want to see if a string contains a zip code (5 digit postal codes), but you don't really care what zip code is in the string. This kind of problem can't be solved usingincludes()orindexOf(). But with regex, we can easily test this: ...
This "simpler" version gives incorrect results if there are two copies of the needle in the string -- then lastIndexOf returns the position of the last copy of that needle, which will be greater than zero, and so will always return False, whether or not the string actually does startWith...
Using a quick regex pre-check improves performs by a big margin if(/^\s*(\{|\[)/.test(str)){ try{ JSON.parse(str) // do something here, or return obj/true }catch(e){ // do nothing or return false } } The regex will check if string opens with a [ or {. This will ...
In JavaScript, the typeof operator is the most used method to check the type of any variable. Alternatively, you can use the typeof() method: let myString = 'John Doe'; typeof myString; // string typeof(myString); // string If used with a string, the typeof operator returns "...
2. 简化 if true...else 对于不包含大逻辑的 if-else 条件,可以使用下面的快捷写法。我们可以简单地使用三元运算符来实现这种简化。 如果有嵌套的条件,可以这么做。 3. if 判断值是否存在 这是我们都在使用的一种常用的简便技巧,在这里仍然值得再提一下。
JavaScript offers many ways to check if a string contains a substring. Learn the canonical way, and also find out all the options you have, using plain JavaScript
How do you check if one string contains a substring in JavaScript?Craig Buckler
To check if two given strings are equal, ignoring the case, in JavaScript, convert both the strings to lowercase, and compare those using equal-to operator