Promise.method

Promise.method(function(...arguments) fn) -> function

Returns a new function that wraps the given function fn. The new function will always return a promise that is fulfilled with the original functions return values or rejected with thrown exceptions from the original function.

This method is convenient when a function can sometimes return synchronously or throw synchronously.

Example without using Promise.method:

MyClass.prototype.method = function(input) {
    if (!this.isValid(input)) {
        return Promise.reject(new TypeError("input is not valid"));
    }

    if (this.cache(input)) {
        return Promise.resolve(this.someCachedValue);
    }

    return db.queryAsync(input).bind(this).then(function(value) {
        this.someCachedValue = value;
        return value;
    });
};

Using the same function Promise.method, there is no need to manually wrap direct return or throw values into a promise:

MyClass.prototype.method = Promise.method(function(input) {
    if (!this.isValid(input)) {
        throw new TypeError("input is not valid");
    }

    if (this.cache(input)) {
        return this.someCachedValue;
    }

    return db.queryAsync(input).bind(this).then(function(value) {
        this.someCachedValue = value;
        return value;
    });
});