How to change console.log() output message depending on if variable is defined or not

Question

Hello I'm new to coding and I wanted to try how far I've learned ( not so much ) So I made this:

var Name = prompt('What is your name?') 
var Name
var Age  = prompt('What is your age?') 
var Age 
const RealAge = 2018 - Age
if (Name && RealAge) {
    console.log("Hello " + Name + " you were born in " + RealAge + ' ...')
} else if (typeof Name == 'undefined') {
    console.log("Please insert your name")
} else if (typeof Age == 'undefined' ) {
    console.log("Please insert your age")
}

I want to know how to make the console.log says "Please insert your name" if you leave the first prompt empty and "Please insert your age" if the second prompt was left empty.

I'm sorry if this is a stupid question but I just started 2 days ago and I'll appreciate your help :)

if (Name === '') and if(Age === '') should do the trick. Also, you should check that before trying to computer RealAge — Federico klez Culloca
– Federico klez Culloca, Commented Mar 2, 2018 at 11:53

Levi Rocha · Accepted Answer · 2018-03-02 12:28:51Z

4

if (Name && RealAge) {
    console.log("Hello " + Name + " you were born in " + RealAge + ' ...')
} else if (!Name) {
    console.log("Please insert your name")
} else if (!Age) {
        console.log("Please insert your age")
}

!Name will evaluate to true if the value is falsy (undefined, null, empty string).

Additionally, as mentioned by Frederico, it would be better to check the values before you do any calculations:

var Name = prompt('What is your name?') 
var Name
var Age  = prompt('What is your age?') 
var Age 
if (!Name) {
    console.log("Please insert your name")
} else if (!Age) {
    console.log("Please insert your age")
} else {
    const RealAge = 2018 - +Age;
    console.log("Hello " + Name + " you were born in " + RealAge + ' ...')
}

If you need to know when both were not entered:

var Name = prompt('What is your name?') 
var Name
var Age  = prompt('What is your age?') 
var Age 
if (!Name) {
    if (!Age) {
        console.log("Please insert your name and age")
    }
    else {
        console.log("Please insert your name")
    }
} else if (!Age) {
    console.log("Please insert your age")
} else {
    const RealAge = 2018 - +Age;
    console.log("Hello " + Name + " you were born in " + RealAge + ' ...')
}

edited Mar 2, 2018 at 12:28

answered Mar 2, 2018 at 11:53

Levi Rocha

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3 Comments

Youssef Ben Gaied Hassine Over a year ago

THANKS so much can you tell me what was wrong besides the undefined thing ?

Levi Rocha Over a year ago

Because Age was an empty string, it was evaluating to 0 in the expression 2018 - Age. Therefore, RealAge was evaluating to 2018.

Youssef Ben Gaied Hassine Over a year ago

Alright then, sorry if I'm asking too much but can you tell me how to set a condition for another console log message if BOTH age and name were not inserted ?

void · Accepted Answer · 2018-03-02 11:55:33Z

2

You do not declare a variable again and again. Also if user does not enter anything in the prompt then its value is "" and not undefined. So just check with === "".

var Name = prompt('What is your name?'); 
var Age  = prompt('What is your age?'); 
const RealAge = 2018 - +Age;
if (Name && RealAge) {
    console.log("Hello " + Name + " you were born in " + RealAge + ' ...')
} else if (Name === '') {
    console.log("Please insert your name")
} else if (Age === '' ) {
    console.log("Please insert your age")
}

edited Mar 2, 2018 at 11:55

answered Mar 2, 2018 at 11:54

void

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3 Comments

Federico klez Culloca Over a year ago

As I said in the comment, it would be useful to check Age before calculationg RealAge.

void Over a year ago

@FedericoklezCulloca Yea logically it would make more sense but programatically absence of check wont break anything.

Federico klez Culloca Over a year ago

yeah, didn't notice the + in +Age.

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