INNER CODE UNIT · JavaScript

optional

gnh1201/welsonjs · app.js:56

var optional = function(f, defaultValue, finalizer, fallback, error) {
    var result = defaultValue;
    var currentError = null;

    try {
        if (typeof f !== "function") {
            throw new Error("The first argument must be a function");
        }
        result = f(error);
    } catch (e) {
        currentError = e;
        if (typeof fallback === "function") {
            result = optional(fallback, defaultValue, null, null, currentError); // call fallback with the error
        }
    } finally {
        if (typeof finalizer === "function") {
            try {
                finalizer(result, currentError);

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