Can a predicate be an object in JavaScript?

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Can a predicate be an object in JavaScript (as in C++)?

For example, is it possible to find the index of an element in an array (with arr.findIndex(pred)) with a predicate like this?

    class Predicate
    {
        constructor()
        {
            this.sum = 0;
        }

        evaluate(elem)
        {
            this.sum += elem;
            return sum > 25;
        }
    }

    const pred = new Predicate();

    const index = arr.findIndex(pred);

EDIT1: If no, what is the easiest way to find the index of an element that makes the sum of it and all the previous elements exceed 25?


It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

Negating Predicate Functions in JavaScript, to be named "isX", such as isEven or isNumber . Negating Predicate Functions in JavaScript. Originally published in the A Drip of JavaScript newsletter. While you may not have heard the term, chances are you've used predicate functions before. A predicate is essentially a function that determines whether something is true or false based on its arguments.


Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

filter() Array Method in JavaScript ← Alligator.io, on X, we sometimes say P is a property of X. When evaluating the composed predicate, if this predicate is false, then the otherpredicate is not evaluated. Any exceptions thrown during evaluation of either predicate are relayed to the caller; if evaluation of this predicate throws an exception, the otherpredicate will not be evaluated. Parameters:


There is no such thing as an evaluate method (that would get invoked when an object gets called like a function) in JavaScript. However, functions themselves are objects and you could even create them with class syntax. It's not very useful though, in JS you would just write a closure to create a function with instance-specific values:

function predicate(max) {
    var sum = 0;
    return function(elem) {
        sum += elem;
        return sum > max;
    };
}

const pred = predicate(25);

const index = arr.findIndex(pred);

What does 'predicate' mean in the context of computer science , represent single argument functions that return a boolean value. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Learn more Get an object from an array on predicate in Javascript [duplicate]


Java Predicate - explaining predicates in Java, A predicate is essentially a function that determines whether something is Suppose that we have a program which deals with cataloging comic book heroes and villains represented as simple objects: As you can see, this is a bit repetitive. A predicate is a condition. "Do this, if this is true". The part in bold is the predicate. In a statement about a callback function in the filter() method as described on JavaScript MDN - Array.prototype.filter, the term predicate is mentioned: Quote:…


Predicates in Javascript by Jack Firth on CodePen, A predicate is a function that takes one item as input and returns They're quite useful for interrogating objects to learn more about can make predicate combinators: functions that build new predicates from simpler ones. The noun ‘apple’ in the above sentence is the object of the sentence because it is being acted upon by the subject ‘He’. The subject ‘He’ is acting (eating) and the object ‘apple’ is being acted upon (is being eaten) by the subject. Examples. She is singing a song. He is writing a letter.


predicate.js, predicate.jsv. 1.0.0. Adding clarity and conciseness to your JS through predicates hosted on GitHub. You can report bugs and discuss features on the issues page or send tweets to @trevor_landau. Returns true if Object.is(a, b). curryable  Predicate in general meaning is a statement about something that is either true or false. In programming, predicates represent single argument functions that return a boolean value. Java Predicate. Predicates in Java are implemented with interfaces.