Question

var MM = '\' + obj[0]['MM '] + '/';

I get two errors while using this code…

missing; before statement and
unterminated string literal

Answer 1

The character \ is “special” because it’s used to allow the use of all printable characters in strings. In your case '\' is not a string composed by the only character \, but the beginning of a string starting with the single quote character '.

For exampe if you want the string Hello Andrea "6502" Griffini you can use single quotes

string1 = 'Hello Andrea "6502" Griffini';

and if you want single quotes in the string you can do the opposite

string2 = "Hello Andrea '6502' Griffini";

But what if you want both kind of quotes in the same string? This is where the escape \ character comes handy:

string3 = "'llo Andrea \"6502\" Griffini";

Basically \ before a quote or double quote in a string tells javascript that the following character is just a regular character, with no special meaning attached to it.

Note that the very same character is also used in regular expressions… for example if you want to look for an open bracket [ you must prefix it with a backslash because [ in a regular expression has a special meaning.

The escape is also used to do the opposite… in a string if you put a backslash in front of a normal character you are telling javascript that that character is indeed special… for example

alert("This is\na test");

In the above line the \n sequence means a newline code, so the message displayed will be on two lines (“This is” and “a test”).

You may now wonder… what if I need a backslash character in my string? Just double it in that case. In your code for example just use '\\'.

Here is a table for the possible meanings of backslash in strings

\"       just a regular double-quote character, it doesn't end the string
\'       just a regular single-quote character, it doesn't end the string
\b       a backspace character (ASCII code 0x08)
\t       a tab character (ASCII code 0x09)
\n       a newline character (ASCII code 0x0A)
\v       a vertical tab character (ASCII code 0x0B)
\f       a form feed character (ASCII code 0x0C)
\r       a carriage return character (ASCII code 0x0D)
\033     the character with ASCII code 033 octal = 27 ("ESC" in this case)
\x41     the character with ASCII code 0x41 = 65 ("A" in this case)
\u05D0   the unicode character 0x05D0 (Aleph from the Hebrew charset)
\\       just regular backslash character, not an escape prefix