How to use String indexOf() to search a sub string in Javascript
Description
indexOf() searches a string and return the position.
indexOf() returns -1
if the substring isn't found.
indexOf() method does the search at the beginning.
Example
var stringValue = "hello world";
console.log(stringValue.indexOf("o")); //4
The code above generates the following result.
Search from the middle
An optional second argument tells where to start with.
var stringValue = "hello world";
console.log(stringValue.indexOf("o", 6)); //7
The code above generates the following result.
Find all occurrences
The following code uses while loop to check the return result. If the
result is not -1 it will keep searching.
var stringValue = "Lorem ipsum dolor sit amet, consectetur adipisicing elit";
var positions = new Array();
var pos = stringValue.indexOf("e");
/*from w w w. j av a 2 s .c om*/
while(pos > -1){
positions.push(pos);
pos = stringValue.indexOf("o", pos + 1);
}
console.log(positions); //3,13,15,29
The code above generates the following result.
Example 2
The following code shows how to use indexOf to validate an email address.
/*w w w . ja va 2 s. c o m*/
var email_add="yourName@yourserver.com";
if (email_add.indexOf("@") == -1)
{
console.log("You need an '@' symbol in your address, please try again.");
}
if (email_add.indexOf(".") == -1)
{
console.log("You need a '.' symbol in your address, please try again.");
}
if ( (email_add.indexOf("@") != -1) && (email_add.indexOf(".") != -1) )
{
console.log("Thanks!");
}
The code above generates the following result.
