CODEWITHSUNDEEP
javascript
Bhasker
Bhasker

Reputation: 197

Typeof Expressions (Number )

The following expressions give peculiar result in JavaScript.

typeof (5 + "7")   // Gives string
typeof (5 - "7")   // Gives number

How do I get the result of the first expression as a number type?

Is there any way to do that without explicitly converting 7 to a number?

Please clarify.

Upvotes: 1

Views: 57

Answers (4)

Manwal
Manwal

Reputation: 23816

Try this way parsing string to integer first. You can parse string implicitly with + or parse to integer with parseInt.

typeof (5 + +"7")

or

typeof (5 + parseInt("7"))

Upvotes: 4

Guffa
Guffa

Reputation: 700362

Yes, there is a way to do that without explicitly converting the string to a number, and that is by implicitly converting the string. You can for example use the + operator, which will cause an implicit conversion of the string to a number, as it can only be applied to a number:

typeof (5 + +"7")

That's not very readable code, though. You are better off with an explicit conversion:

typeof (5 + parseFloat("7"))

Upvotes: 1

adeneo
adeneo

Reputation: 318212

The plus sign in javascript adds numbers together, but it also concatenates strings, and when one of the values being added together is a string, the latter is done, regardless of what the other values are.

The minus sign subtracts, and you can't subtract a string from a string, so it's only meaning is to subtract numbers

So in other words

5 + "7" === "57" // string
5 + 7   === 12   // number
5 - "7" === -2   // number

so no, you'd have to convert the string to a number to be able to add it to another number

5 - ( parseInt("7", 10) ) === -2   // number
5 - ( +"7" ) === -2   // number

Upvotes: 0

atmd
atmd

Reputation: 7490

The only way you'd be able to so that is by converting the string to a number

typeof (5 + parseInt("7"))

N.b. that's if you are using the plus operator, multiply/divide/minus work differently and will convert the string type to a number (unless NaN)

Upvotes: 0

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