Function assert

jsonpath.js:215–220

(condition, message)

    // Do NOT use this to enforce a certain condition on any user input.

    function assert(condition, message) {
        /* istanbul ignore if */
        if (!condition) {
            throw new Error('ASSERT: ' + message);
        }
    }

    function isDecimalDigit(ch) {
        return (ch >= 48 && ch <= 57);   // 0..9