The hasIndices accessor property of RegExp instances returns whether or not the d flag is used with this regular expression.
Description
RegExp.prototype.hasIndices has the value true if the d flag was used; otherwise, false. The d flag indicates that the result of a regular expression match should contain the start and end indices of the substrings of each capture group. It does not change the regex's interpretation or matching behavior in any way, but only provides additional information in the matching result.
This flag primarily affects the return value of exec(). If the d flag is present, the array returned by exec() has an additional indices property as described in the exec() method's return value. Because all other regex-related methods (such as String.prototype.match) call exec() internally, they will also return the indices if the regex has the d flag.
The set accessor of hasIndices is undefined. You cannot change this property directly.
Examples
There's a more detailed usage example at Groups and backreferences > Using groups and match indices.
Using hasIndices
const str1 = "foo bar foo";
const regex1 = /foo/dg;
console.log(regex1.hasIndices); // true
console.log(regex1.exec(str1).indices[0]); // [0, 3]
console.log(regex1.exec(str1).indices[0]); // [8, 11]
const str2 = "foo bar foo";
const regex2 = /foo/;
console.log(regex2.hasIndices); // false
console.log(regex2.exec(str2).indices); // undefined