less.js/lib/less/tree/javascript.js

var JsEvalNode = require("./js-eval-node"),
    Dimension = require("./dimension"),
    Quoted = require("./quoted"),
    Anonymous = require("./anonymous");

var JavaScript = function (string, escaped, index, currentFileInfo) {
    this.escaped = escaped;
    this.expression = string;
    this.index = index;
    this.currentFileInfo = currentFileInfo;
};
JavaScript.prototype = new JsEvalNode();
JavaScript.prototype.type = "JavaScript";
JavaScript.prototype.eval = function(context) {
    var result = this.evaluateJavaScript(this.expression, context);

    if (typeof result === 'number') {
        return new Dimension(result);
    } else if (typeof result === 'string') {
        return new Quoted('"' + result + '"', result, this.escaped, this.index);
    } else if (Array.isArray(result)) {
        return new Anonymous(result.join(', '));
    } else {
        return new Anonymous(result);
    }
};

module.exports = JavaScript;