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Escape Sequences in String Literals Using JavaScript

By Martin Schaeferle

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One of the fundamental tasks handled by programming languages is to temporarily store and manipulate bits of data in memory, mostly strings and numbers, but often also dates and other special data types, called values. One of the defining characteristics of a programming language is the data types it supports and the features it has for working with those types. A language's types define the kinds of values you can represent and work with.

When you need to save a value for later use in the program, you can define a variable and store the value in it. A variable is a symbolic name for the value that you store in memory, and lets you refer to the value by name and, over the course of program execution, assign different values to the same variable. Following is an explanation of Escape Sequences in String Literals and their use in JavaScript.

Escape Sequences in String Literals

When you need to include any of a number of characters that have special meaning within a string literal, you can create an escape sequence using a backslash to identify the special character. For example, if you absolutely must include the type of quote used as a string delimiter within the string, you can create an escape sequence as in the following string literal. By making it an escape sequence, the single quote will appear within the string, even though that is also the string delimiter.

'"Don't use that food to feed the dog," she said. "It's been recalled by the manufacturer."

The reason why this is called an escape sequence is that the backslash causes an escape from the usual interpretation of the single quote character in the previous example. Table 2 lists the available JavaScript escape sequences. If you include the backslash in front of any other character than those shown in Table 2, JavaScript will ignore the backslash, such as if you include * in a string literal.

This is risky however, because future versions of JavaScript could define new escape sequences that would give meaning to the sequence in your code. As unlikely as that may seem, it's best to avoid the possibility of broken code in the future. The following code demonstrates some of these escape sequences. Some lines are broken in random places to fit on the page, but each console.log statement should appear on a single line in a code file. Figure 3 shows the results in the Console panel.

console.log('"Don't use that food to feed the dog," she said. "It's been recalled by the manufacturer."'); console.log("tStart this line indented a bit."); console.log("The backslash (\) character is the escape sequence marker in JavaScript."); console.log("You can use the newlinenescape sequence (\n) to break anstring over multiple lines."); console.log("The copyright symbol is xa9 and pi is u03c0.");

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Figure 3. The results in the Console panel of running sample escape sequence code.

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Martin Schaeferle

Martin Schaeferle has taught IT professionals nationwide to develop applications using Visual Basic, Microsoft SQL Server, ASP, and XML. He has been a featured speaker at Microsoft Tech-Ed and the Microsoft NCD Channel Summit, and he specializes in developing Visual Basic database applications, COM-based components, and ASP-based Web sites. In addition to writing and presenting technical training content, Martin is also LearnNowOnline's vice president of technology.


This blog entry was originally posted July 19, 2012 by Martin Schaeferle

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