Enumerate regular expressions via UglifyJS

Question

I have some JavaScript code, from which I need to find start+end indexes of every literal regular expression.

How can such information be extracted from UglifyJS?

Answer 1

I got this ultimately useful link to the UglifyJS author's blog post, which pointed me in the right direction. Based on that blog I was able to modify my enumeration code to the following:

function enumRegEx(parsed) {
    var result = [];
    parsed.walk(new uglify.TreeWalker(function (obj) {
        if (obj instanceof uglify.AST_RegExp) {
            result.push({
                startIdx: obj.end.col,
                endIdx: obj.end.endcol
            });
        }
    }));
    return result;
}

Not only this thing is shorter and works the same, but its processing speed is almost instant, within 10ms, which puts the previous result (430ms) to shame.

Now that is the result I was looking for! :)

UPDATE: In the end though, I found out that for this particular task esprima is a much better choice. It is much faster and has full ES6 support, unlike UglifyJS.

The very same task done via esprima, thanks to the excellent support from Ariya Hidayat:

function parseRegEx(originalCode) {
    var result = [];
    esprima.tokenize(originalCode, {loc: true, range: true}, function (obj) {
        if (obj.type === 'RegularExpression') {
            result.push({
                startIdx: obj.range[0],
                endIdx: obj.range[1]
            });
        }
    });
    return result;
}

As you can see, with esprima you do not even need to parse the code, you pass in the original code instead, which esprima will only tokenize, which is way faster.