Javascript string method
- 1. Prof. Neeraj Bhargava Kapil Chauhan Department of Computer Science School of Engineering & Systems Sciences MDS University, Ajmer
- 2. String Length The length property returns the length of a string: Example var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; var sln = txt.length; Output: The length property returns the length of a string: 26 Finding a String in a String The indexOf() method returns the index of (the position of) the first occurrence of a specified text in a string: Example var str = "Please locate where 'locate' occurs!"; var pos = str.indexOf("locate"); Output: The indexOf() method returns the position of the first occurrence of a specified text: 7
- 3. The lastIndexOf() method returns the index of the last occurrence of a specified text in a string: Example var str = "Please locate where 'locate' occurs!"; var pos = str.lastIndexOf("locate"); Output:The lastIndexOf() method returns the position of the last occurrence of a specified text:21 Both indexOf(), and lastIndexOf() return -1 if the text is not found.
- 4. Example var str = "Please locate where 'locate' occurs!"; var pos = str.lastIndexOf("John"); Output: -1 Both methods accept a second parameter as the starting position for the search:
- 5. The search() method searches a string for a specified value and returns the position of the match: Example var str = "Please locate where 'locate' occurs!"; var pos = str.search("locate"); Output: The search() method returns the position of the first occurrence of a specified text in a string: 8
- 6. There are 3 methods for extracting a part of a string: slice(start, end) substring(start, end) substr(start, length)
- 7. slice() extracts a part of a string and returns the extracted part in a new string. The method takes 2 parameters: the start position, and the end position (end not included). This example slices out a portion of a string from position 7 to position 12 (13-1): Example var str = "Apple, Banana, Kiwi"; var res = str.slice(7, 13); The result of res will be: Banana
- 8. substring() is similar to slice(). The difference is that substring() cannot accept negative indexes. Example var str = "Apple, Banana, Kiwi"; var res = str.substring(7, 13); The result of res will be: Banana
- 9. substr() is similar to slice(). The difference is that the second parameter specifies the length of the extracted part. Example var str = "Apple, Banana, Kiwi"; var res = str.substr(7, 6); The result of res will be: Banana
- 10. A string is converted to upper case with toUpperCase(): Example var text1 = "Hello World!"; var text2 = text1.toUpperCase(); Output: HELLO WORLD! A string is converted to lower case with toLowerCase(): Example var text1 = "Hello World!"; var text2 = text1.toLowerCase(); Output: hello world!