RegExp.leftContext ($`)
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The non-standard leftContext property is a static and read-only property of regular expressions that contains the substring preceding the most recent match. RegExp.$`
is an alias for this property.
Description
The leftContext
property is static, it is not a property of an individual regular expression object. Instead, you always use it as RegExp.leftContext
or RegExp['$`']
.
The value of the leftContext
property is read-only and modified whenever a successful match is made.
You can not use the shorthand alias with the dot property accessor (RegExp.$`
), because the parser expects a starting template string in that case and a SyntaxError
is thrown. Use the bracket notation for property access.
Examples
Using leftContext and $`
var re = /world/g;
re.test('hello world!');
RegExp.leftContext; // "hello "
RegExp['$`']; // "hello "
Specifications
No specification found
No specification data found for javascript.builtins.RegExp.leftContext
.
Check for problems with this page or contribute a missing spec_url
to mdn/browser-compat-data. Also make sure the specification is included in w3c/browser-specs.
Browser compatibility
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