Check if several values are numbers

Question

I'm making a simple quadratic equation app, the user should enter a three number first: a, b and c.

The first step is checking if all input values are numbers, unfortunately, the function I wrote isn't working. How can I rewrite my function so it console.log 'Input valid data' if the input value is not a number.

Here is my code: 

const a_number = parseFloat(prompt("Please, enter a-number", '0'));
const b_number = parseFloat(prompt("Please, enter b-number", '0'));
const c_number = parseFloat(prompt("Please, enter c-number", '0'));
console.log(a_number, b_number, c_number);
ValidInput(a_number, b_number, c_number);

function ValidInput (a, b, c) {
    if (a || b || c) {
        return 
    } else {
        console.log('Invalid input data');
    }
}

Please use is isNaN provided by javascript. This link be helpful for you w3schools.com/jsref/jsref_isnan.asp — Ankur Shah
– Ankur Shah, Commented Feb 4, 2019 at 7:20

Riad · Accepted Answer · 2019-02-04 07:21:57Z

3

May use is isNaN or typeof function:

 function ValidInput (a, b, c) {
    if (isNaN(a) || isNaN(b) || isNaN(c)) {
       console.log('Invalid input data');
    } else {
       return
    }
  }

answered Feb 4, 2019 at 7:21

Riad

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2 Comments

manish kumar Over a year ago

isNaN(null) returns false . which is incorrect in case of number. use typeof a ==="number" instead

manish kumar Over a year ago

for this usecase we wont get null since parseFloat(null) = NaN

Sebastian G. Marinescu · Accepted Answer · 2019-02-04 07:38:00Z

2

You could write your valdiator-function like this:

function ValidInput(a, b, c) {
    var argArr = Array.from(arguments);
    return !argArr.some(isNaN);
}

answered Feb 4, 2019 at 7:38

Sebastian G. Marinescu

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Comments

adiga · Accepted Answer · 2019-02-04 07:22:33Z

1

Use isNaN

const a_number = parseFloat(prompt("Please, enter a-number", '0'));
const b_number = parseFloat(prompt("Please, enter b-number", '0'));
const c_number = parseFloat(prompt("Please, enter c-number", '0'));
console.log(a_number, b_number, c_number);
ValidInput(a_number, b_number, c_number);

function ValidInput (a, b, c) {
    if (isNaN(a) || isNaN(b) || isNaN(c)) {
       console.log('Invalid input data');
    } else {
        // do something
    }
}

Mind you, your code works even if you enter something which starts with a number and then has some non-numeric characters. For Example, if you type 5.5somethingelse, parseFloat takes the numbers until it hits a non-numeric value. It gets 5.5

answered Feb 4, 2019 at 7:22

adiga

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Comments

The fourth bird · Accepted Answer · 2019-02-04 08:05:34Z

0

You might also add the parameters your want to test to an array and use some and isNaN:

ValidInput = (a, b, c) => ![a,b,c].some(isNaN);

For example:

ValidInput = (a, b, c) => ![a, b, c].some(isNaN);

if (!ValidInput(1, "a", 3)) {
  console.log('Invalid input data');
}

edited Feb 4, 2019 at 8:05

answered Feb 4, 2019 at 7:53

The fourth bird

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