Question 175881 in Javascript Question posted in
A very good W3school tutorial can be found here.

Is there a way to check if an object is array-like but not an array in Javascript?

We can check whether a variable is array-like or array by Checking if an object is array-like.

How to check if a variable is array-like but not an array?

Update 1:

What I have tried so far is:

const car = { type: "Fiat", model: "500", color: "white" };
const cars = ["Saab", "Volvo", "BMW"];

function sum(a, b, c) {
    console.log(Array.prototype.isPrototypeOf(arguments));
    return a + b + c;
}

console.log(Array.prototype.isPrototypeOf(car));
console.log(Array.prototype.isPrototypeOf(cars));
result = sum(1, 2, 3)

I have use function sum because the documentation says:

arguments is an array-like object

So far it yields correct result. Please let me know whether I am on the right track.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    OP Here, The answer is derived from the referred question.

    var array = [];
array['test1'] = 'property';
array['test2'] = 'property';
array[0] = 'value';
array[1] = 'value';
array[-1] = 'value';
array[1.5] = 'float';
array[001] = 'float';

const car = { type: "Fiat", model: "500", color: "white" };
const cars = ["Saab", "Volvo", "BMW"];

function args_of_func(a, b, c) {
    return isArrayLike(arguments);
}

function isArrayLike(item) {
    if (!Array.isArray(item) &&
    !(item instanceof Array) &&
    !Array.prototype.isPrototypeOf(item) &&
    Object.prototype.toString.call(item) !== '[object Array]' &&
    Number.isInteger(item.length) &&
    item.hasOwnProperty("length") &&
    Array.prototype.hasOwnProperty.call(item, "length"))
    {
        return true;
    }
    return false;
}

console.log("For Object");
console.log(isArrayLike(car));
console.log("For Array");
console.log(isArrayLike(cars));
console.log("For Array-like");
console.log(args_of_func(1, 2, 3));

    isArrayLike will return true for only array-like objects, and false for arrays or other type of objects.


  2. 0

    arguments in a function is an object with keys and values you do not need to check if it is array like.

    function sum(a,b,c){
  console.log(typeof arguments, arguments);

}

const car = { type: "Fiat", model: "500", color: "white" };
const cars = ["Saab", "Volvo", "BMW"];

sum(1,2,3)
sum(car);
sum(cars);
sum(...cars);

    If you want to sum every value passed to function sum just loop throuht arguments using for..in loop

    function sum(){
  let total = 0;
  for(const key in arguments){
    total += arguments[key];
  }
  return total;
}

console.log(sum(1,2,3));

// strings as arguments
const cars = ["Saab", "Volvo", "BMW"];
console.log(...cars);

    Make sure every arguments[key] is a number which can be summed otherwise strings will be concatenated

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