String methods help you to work with strings.
String Methods and Properties
Primitive values, like "John Doe", cannot have properties or methods (because they are not objects).
But with JavaScript, methods and properties are also available to primitive values, because JavaScript treats primitive values as objects when executing methods and properties.
JavaScript String Length
The length property returns the length of a string:
Example
let txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
let length = txt.length;
Extracting String Parts
There are 3 methods for extracting a part of a string:
slice(start, end)substring(start, end)substr(start, length)
JavaScript String slice()
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
let str = "Apple, Banana, Kiwi";
let part = str.slice(7, 13);
Note
JavaScript counts positions from zero.
First position is 0.
Second position is 1.
If a parameter is negative, the position is counted from the end of the string.
This example slices out a portion of a string from position -12 to position -6:
Example
let str = "Apple, Banana, Kiwi";
let part = str.slice(-12, -6);
If you omit the second parameter, the method will slice out the rest of the string:
Example
let part = str.slice(7);
or, counting from the end:
Example
let part = str.slice(-12);
JavaScript String substring()
substring() is similar to slice().
The difference is that substring() cannot accept negative indexes.
Example
let str = "Apple, Banana, Kiwi";
let part = str.substring(7, 13);
If you omit the second parameter, substring() will slice out the rest of the
string.
JavaScript String substr()
substr() is similar to slice().
The difference is that the second parameter specifies the length of the extracted part.
Example
let str = "Apple, Banana, Kiwi";
let part = str.substr(7, 6);
If you omit the second parameter, substr() will slice out the rest of the
string.
Example
let str = "Apple, Banana, Kiwi";
let part = str.substr(7);
If the first parameter is negative, the position counts from the end of the string.
Example
let str = "Apple, Banana, Kiwi";
let part = str.substr(-4);
Replacing String Content
The replace() method replaces a specified value with another
value in a string:
Example
let text = "Please visit Microsoft!";
let newText = text.replace("Microsoft", "W3Schools");
Note
The replace() method does not change the string it is called on.
The replace() method returns a new string.
By default, the replace() method replaces only the first match:
Example
let text = "Please visit Microsoft and Microsoft!";
let newText = text.replace("Microsoft", "W3Schools");
By default, the replace() method is case sensitive. Writing MICROSOFT (with
upper-case) will not work:
Example
let text = "Please visit Microsoft!";
let newText = text.replace("MICROSOFT", "W3Schools");
To replace case insensitive, use a regular expression with an /i flag (insensitive):
Example
let text = "Please visit Microsoft!";
let newText = text.replace(/MICROSOFT/i, "W3Schools");
Note
Regular expressions are written without quotes.
To replace all matches, use a regular expression with a /g flag (global match):
Example
let text = "Please visit Microsoft and Microsoft!";
let newText = text.replace(/Microsoft/g, "W3Schools");
Note
You will learn a lot more about regular expressions in the chapter JavaScript Regular Expressions.
Converting to Upper and Lower Case
A string is converted to upper case with toUpperCase():
A string is converted to lower case with toLowerCase():
JavaScript String toUpperCase()
Example
let text1 = "Hello World!";
let text2 = text1.toUpperCase();
JavaScript String toLowerCase()
Example
let text1 = "Hello World!"; // String
let text2 = text1.toLowerCase(); // text2 is text1
converted to lower
JavaScript String concat()
concat() joins two or more strings:
Example
let text1 = "Hello";
let text2 = "World";
let text3 = text1.concat(" ", text2);
The concat() method can be used instead of the plus operator.
These two lines do the same:
Example
text = "Hello" + " " + "World!";
text = "Hello".concat(" ", "World!");
Note
All string methods return a new string. They don't modify the original string.
Formally said:
Strings are immutable: Strings cannot be changed, only replaced.
JavaScript String trim()
The trim() method removes whitespace from both sides of a string:
Example
let text1 = " Hello World! ";
let text2 = text1.trim();
JavaScript String Padding
ECMAScript 2017 added two String methods: padStart
and padEnd to support padding at the beginning and at the end of a string.
JavaScript String padStart()
Example
let text = "5";
let padded = text.padStart(4,0);
Browser Support
padStart() is an ECMAScript 2017 feature.
It is supported in all modern browsers:
| Chrome | Edge | Firefox | Safari | Opera |
| Yes | Yes | Yes | Yes | Yes |
padStart() is not supported in Internet Explorer.
JavaScript String padEnd()
Example
let text = "5";
let padded = text.padEnd(4,0);
Browser Support
padEnd() is an ECMAScript 2017 feature.
It is supported in all modern browsers:
| Chrome | Edge | Firefox | Safari | Opera |
| Yes | Yes | Yes | Yes | Yes |
padEnd() is not supported in Internet Explorer.
Extracting String Characters
There are 3 methods for extracting string characters:
charAt(position)charCodeAt(position)- Property access [ ]
JavaScript String charAt()
The charAt() method returns the character at a specified
index (position) in a string:
Example
let text = "HELLO WORLD";
let char = text.charAt(0);
JavaScript String charCodeAt()
The charCodeAt() method returns the unicode of the character
at a specified index in a string:
The method returns a UTF-16 code (an integer between 0 and 65535).
Example
let text = "HELLO WORLD";
let char = text.charCodeAt(0);
Property Access
ECMAScript 5 (2009) allows property access [ ] on strings:
Example
let text = "HELLO WORLD";
let char = text[0];
Note
Property access might be a little unpredictable:
- It makes strings look like arrays (but they are not)
- If no character is found, [ ] returns undefined, while charAt() returns an empty string.
- It is read only. str[0] = "A" gives no error (but does not work!)
Example
let text = "HELLO WORLD";
text[0] = "A"; // Gives no error, but does not work
Converting a String to an Array
If you want to work with a string as an array, you can convert it to an array.
JavaScript String split()
A string can be converted to an array with the split() method:
Example
text.split(",") // Split on commas
text.split(" ") // Split on spaces
text.split("|") // Split on pipe
If the separator is omitted, the returned array will contain the whole string in index [0].
If the separator is "", the returned array will be an array of single characters:
Example
text.split("")
Complete String Reference
For a complete String reference, go to:
Complete JavaScript String Reference.
The reference contains descriptions and examples of all string properties and methods.