javascript - get current line number (in current script)

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// Hint: JavaScript API doesn't support get current line operation, but it is possible to do it using some trick.


var NEWLINE_EXPRESSION = /\r\n|\n/g;
var POSITION_EXPRESSION = /:(\d+):\d+\)?$/g;

function splitLines(text) {
    return text.split(NEWLINE_EXPRESSION);
}

function findMatching(expression, text) {
    expression.lastIndex = 0;
    return expression.exec(text);
}

function getLine() {
    var error = new Error();
    if (!error.stack) {
        try {
            throw error;  // error is thrown to get stack
        } catch (e) {
            if (!e.stack) {
                return null;
            }
        }
    }
    var lines = splitLines(error.stack);
    for (var i = 0, j = 0; i < lines.length; i += 1) {
        var match = findMatching(POSITION_EXPRESSION, lines[i]);
        if (match) {
            if (j === 1) {
                return parseInt(match[1]);
            }
            j += 1;
        }
    }
    return null;
}


// Usage example:

console.log(getLine());  // 43
console.log(getLine());  // 44
console.log(getLine());  // 45
console.log(getLine());  // 46
console.log(getLine());  // 47


// Tested under:
//  - Google Chrome
//  - Mozilla Firefox
//  - Microsoft Edge
//  - Microsoft IE10+
//  - Apple Safari
//  - Node.js