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JavaScript substr() | Extract Substring from a String
The JavaScript substr() method is used to extract substring from specified position in specified string. For example:
<!DOCTYPE html> <html> <body> <p id="xyz"></p> <script> let myString = "JavaScript is Fun. Is not it?"; let mySubString = myString.substr(19); document.getElementById("xyz").innerHTML = mySubString; </script> </body> </html>
Since indexing starts with 0. Therefore in the string "JavaScript is Fun. Is not it?"
- 'J' is at index no.0
- 'a' is at index no.1
- 'v' is at index no.2
- and so on
Similar 'I' is at index no.19. Therefore substring starting from index no.19 was extracted from the string. That is, after the index no.18, remaining or all characters of the specified string was extracted.
JavaScript substr() Syntax
The syntax of substr() method in JavaScript is:
string.substr(startIndex, numberOfCharacters)
The startIndex argument is required. Whereas the numberOfCharacters argument is optional and its default value is the length of the string (string.length - 1).
The numberOfCharacters argument refers to a number, used when we need to extract only particular number of characters from the specified startIndex position. For example:
<!DOCTYPE html> <html> <body> <p id="xyz"></p> <script> let myString = "JavaScript is Fun. Is not it?"; let mySubString = myString.substr(19, 2); document.getElementById("xyz").innerHTML = mySubString; </script> </body> </html>
Note: The string.substr(0, 1) returns the first character of the string.
Note: The string.substr(string.length-1, 1) returns the last character of the string.
Note: The string.substr(-3, 3) returns the last 3 characters of the string.
Note: The string.substr(-7, 3) returns the 3 characters starting from the seventh position from last. For example:
<!DOCTYPE html> <html> <body> <p id="xyz"></p> <script> let myString = "JavaScript is Fun. Is not it?"; let mySubString = myString.substr(-7, 3); document.getElementById("xyz").innerHTML = mySubString; </script> </body> </html>
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