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leftContext Property ($`)

Returns the characters from the beginning of a searched string up to the position before the beginning of the last match. Read-only.



Required. The global RegExp object.


The initial value of the leftContext property is an empty string. The value of the leftContext property changes whenever a successful match is made.

Note   The properties of the RegExp object are not available when running in fast mode, the default for JScript .NET. To compile a program from the command line that uses these properties, you must turn off the fast option by using /fast-. It is not safe to turn off the fast option in ASP.NET because of threading issues.


The following example illustrates the use of the leftContext property:

var s;                                //Declare variable.
var re = new RegExp("d(b+)(d)","ig"); //Regular expression pattern.
var str = "cdbBdbsbdbdz";             //String to be searched.
var arr = re.exec(str);               //Perform the search.
s = "$1 returns: " + RegExp.$1 + "\n";
s += "$2 returns: " + RegExp.$2 + "\n";
s += "$3 returns: " + RegExp.$3 + "\n";
s += "input returns : " + RegExp.input + "\n";
s += "lastMatch returns: " + RegExp.lastMatch + "\n";
s += "leftContext returns: " + RegExp.leftContext + "\n";
s += "rightContext returns: " + RegExp.rightContext + "\n"; 
s += "lastParen returns: " + RegExp.lastParen + "\n";
print(s);                            //Return results.

After compiling this program with the /fast- option, the output of this program is:

$1 returns: bB
$2 returns: d
$3 returns:
input returns : cdbBdbsbdbdz
lastMatch returns: dbBd
leftContext returns: c
rightContext returns: bsbdbdz
lastParen returns: d


Version 5.5

See Also

$1...$9 Properties | index Property | input Property ($_) | lastIndex Property | lastMatch Property ($&) | lastParen Property ($+) | rightContext Property ($')

Applies To: RegExp Object