How does larger and smaller Javascript string checking work?

Question

If you perform the condition '15000' > '100000' the result will be true

If you perform the condition 15000 > 100000 the result will be false

If you perform the condition '15000' > '200000' the result will be false

The question here is to understand the operation of javascript in the comparison of string and not know the right way to compare.

Can anyone explain?

Answer 1

When there is a comparison '15000' > '100000', imagine that alphabetically the value 15000 is greater than 100000.

As if it were a classroom call list in which names are ordered alphabetically, this comparison would roughly be this way.

1º '10000'
2º '19520000'
3º '2'
...

Agree to the observation of @fernandosavio on the reference I made earlier, I suggest this site which has a more detailed explanation of string comparison.

Answer 2

Javascript compares letter by letter, using the coding dictionary that JS uses (Unicode).

Hence, strings are not compared on a whole, but are divided and each character is compared individually, until one is larger or smaller than the other.

For example:

'A' > 'Z'

Would return false, in view of the fact that, in the Unicode dictionary, the decimal code of the letters are:

'A'.charCodeAt(0) // 65

'Z'.charCodeAt(0) // 90

Soon, Z is greater than A.

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Thus, when comparing strings carro > cachorro, we have true, since the comparison is made as follows:

1. c > c ⇒ false, therefore, it is not possible to determine which character is larger.
2. a > a ⇒ false, therefore, it is not possible to determine which character is larger.
3. r > c ⇒ true, what ends the comparison, assessing that carro is greater than cachorro.

It’s like, underneath the scenes, Javascript does this:

const char1 = 'g'
const char2 = 'c'

console.log(
  char1 > char2
)

console.log(
  char1.charCodeAt(0) > char2.charCodeAt(0)
)

You can check the Unicode table here.

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My response was immensely based in this section the excellent documentation of the Javascript website.info.