Function evalRPN

javascript/0150-evaluate-reverse-polish-notation.js:7–21

(tokens, index = 0)

 * @return {number}
 */
var evalRPN = function (tokens, index = 0) {
    while (1 < tokens.length) {
        /* Time O(N) */
        const isOperation = () => tokens[index] in OPERATORS;
        while (!isOperation()) index++; /* Time O(N) */

        const value = performOperation(tokens, index);

        tokens[index] = value;
        tokens.splice(index - 2, 2); /* Time O(N) */
        index--;
    }

    return tokens[0];
};

var OPERATORS = {
    '+': (a, b) => a + b,