Now that we understand the basic usage of the indexOf() method in JavaScript let's explore some practical use cases. Checking if a String Contains a Specific Value We can use the indexOf() method to check if a string contains a specific value. If the method returns -1, it means that...
TheindexOf()method returns the position of the first occurrence of a value in a string. TheindexOf()method returns -1 if the value is not found. TheindexOf()method is case sensitive. See Also: The lastIndexOf() Method The search() Method ...
log("'" + searchString + "' was not found in the string."); } 完整示例代码 javascript const exampleString = "Hello, this is a test string to demonstrate indexOf method."; const searchString = "test"; const index = exampleString.indexOf(searchString); if (index !== -1) { ...
"Programiz JavaScript".indexOf("",0);// returns 0"Programiz JavaScript".indexOf("",3);// returns 3// string length here is 20"Programiz JavaScript".indexOf("",25);// returns 20"Programiz JavaScript".indexOf("",21);// returns 20 Example 1: Using indexOf() method varstr ="JavaScri...
ThelastIndexOf()method returns the index (position) of the last occurrence of a specified value in a string. ThelastIndexOf()method searches the string from the end to the beginning. ThelastIndexOf()method returns the index from the beginning (position 0). ...
String 的 indexOf() 方法在字符串中搜索指定子字符串,并返回其第一次出现的位置索引。它可以接受一个可选的参数指定搜索的起始位置,如果找到了指定的子字符串,则返回的位置索引大于或等于指定的数字。
Here, we have passed"Python"as asubstr. Since"Python"is not found in the"I love JavaScript"string, the method returns-1. Example 4: lastIndexOf() For Case-Sensitive Search ThelastIndexOf()method is case sensitive. For example: varstr ="I love JavaScript"; ...
// get users method getUsers(id: String){ return this._http.get<any[]>(this.url + 'getAllChallenge').subscribe( (users)=>{ this.users=users; this.checkExist= this.users.indexOf(id) if(this.checkExist==-1){ alert("this id you typed doesn't exist in our array") ...
Learn how to simplify the JavaScript indexOf method for efficient searching and manipulation. Get clear explanations and examples here!
IndexOf(String substring) This method returns the index of the first character of the substring passed as parameter to it. If the specified substring is not present in the string, the returned index would be -1. IndexOf(String substring, int fromindex) ...