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C # tutorial
JavaScript strings are for storing and manipulating text
To find the length of a string, use the built-in length property:
let text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
let length = text.length;
Because strings must be written within quotes, JavaScript will misunderstand this string:
let text = "We are the so-called "Vikings" from the north.";
The string will be chopped to "We are the so-called ".
The solution to avoid this problem, is to use the backslash escape character.
The backslash (\) escape character turns special characters into string characters:
| Code | Result | Description |
|---|---|---|
| \' | ' | Single quote |
| \" | " | Double quote |
| \\ | \ | Backslash |
The sequence \" inserts a double quote in a string:
let text = "We are the so-called \"Vikings\" from the north.";
The sequence \' inserts a single quote in a string:
let text= 'It\'s alright.';
The sequence \\ inserts a backslash in a string:
let text = "The character \\ is called backslash.";
Six other escape sequences are valid in JavaScript:
| Code | Result |
|---|---|
| \b | Backspace |
| \f | Form Feed |
| \n | New Line |
| \r | Carriage Return |
| \t | Horizontal Tabulator |
| \v | Vertical Tabulator |
The 6 escape characters above were originally designed to control typewriters, teletypes, and fax machines. They do not make any sense in HTML.
For best readability, programmers often like to avoid code lines longer than 80 characters.
If a JavaScript statement does not fit on one line, the best place to break it is after an operator:
document.getElementById("demo").innerHTML =
"Hello Dolly!";
You can also break up a code line within a text string with a single backslash:
document.getElementById("demo").innerHTML =
"Hello \
Dolly!";
The \ method is not the preferred method. It might not have universal support.
Some browsers do
not allow spaces behind the \ character.
A safer way to break up a string, is to use string addition:
document.getElementById("demo").innerHTML = "Hello " +
"Dolly!";
You cannot break up a code line with a backslash:
document.getElementById("demo").innerHTML = \
"Hello Dolly!";
Normally, JavaScript strings are primitive values, created from literals:
let x = "John";
But strings can also be defined as objects with the keyword new:
let y = new String("John");
let x = "John";
let y = new String("John");
Do not create Strings objects.
The new keyword complicates the code and slows down execution speed.
String objects can produce unexpected results:
When using the == operator, x and y are equal:
let x = "John";
let y = new String("John");
When using the === operator, x and y are not equal:
let x = "John";
let y = new String("John");
Note the difference between (x==y) and (x===y).
(x == y) true or false?
let x = new String("John");
let y = new String("John");
(x === y) true or false?
let x = new String("John");
let y = new String("John");
Comparing two JavaScript objects always returns false.
For a complete String reference, go to our:
Complete JavaScript String Reference.
The reference contains descriptions and examples of all string properties and methods.
Use the length property to alert the length of txt.
let txt = "Hello World!"; let x = ; alert(x);