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JavaScript

Posted by Sebastian Nitu
Sebastian Nitu
8,616 Points

Some help with conditionals in JavaScript, please?

Hello,

So I was playing around with the code, you know, to make it "sink in" better. I was just about to pass on to "loops" when i encountered this strange situation:

If I execute this code, regardless of the string value assigned to name it will pass it to the if block even though the value is not "David".

var name = prompt("what is your name?");

if (name = "David") {

alert("Howdy partner!");

} else {

alert("Hello " + name + ", want some cake?");

console.log(name + " wants some cake!");

}

The strange part is that if I use a "not equal to" operator "!=" it works but different. If the name is not David, then it will go to say "Howdy partner!" but if the name is "David" it will say "Hello "David" want some cake?"

var name = prompt("what is your name?");

if (name != "David") {

alert("Howdy partner!");

} else {

alert("Hello " + name + ", want some cake?");

console.log(name + " wants some cake!");

}

The question here is, why isn't the first example working?

Why is the second example working?

How should I have done this?

4 Answers

Daniel Matthew
Daniel Matthew
2,625 Points
Daniel Matthew
Daniel Matthew
2,625 Points

I couldn't tell you the particulars, but your code should be looking to compare rather than assign. So your code becomes 

if (name == "David") {}

(or even if (name === "David"){})

Sebastian Nitu
Sebastian Nitu
8,616 Points
Sebastian Nitu
Sebastian Nitu
8,616 Points

Thanks Daniel, what is the difference between "==" and "==="?

Thanks once again!

Rick Yentzer
Rick Yentzer
5,885 Points
Rick Yentzer
Rick Yentzer
5,885 Points

The difference between == and === is that == will do type conversion. For instance:

if (2 == "2") {
  // this code WILL run
}

Even though typeof(2) = number and typeof("2") = string, when using == JS will coerce the data type in order to compare the values if possible.

if (2 === "2") {
  // this code WILL NOT run
}

The === is for strict comparison. It will not attempt to convert data types. Therefore 2 != "2";

Here is a good explanation: http://www.impressivewebs.com/why-use-triple-equals-javascipt/

Daniel Matthew
Daniel Matthew
2,625 Points
Daniel Matthew
Daniel Matthew
2,625 Points

Thanks Rick - you were able to put that much more succinctly than I.