javascript - Starting Class or Method Names with Numbers, Why Not? - Stack Overflow

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I recently was quickly shortening some method names in a JavaScript file and ran into a problem when I converted one method name:

Before:

RefreshSevenDayGrid(){
    // some stuff
}

After:

7Day() {    
    // some stuff
}

I quickly discovered that the javascript no longer worked. I heard from several people that numbers should never be used for method or class names. Is there ever an exception to this?

I recently was quickly shortening some method names in a JavaScript file and ran into a problem when I converted one method name:

Before:

RefreshSevenDayGrid(){
    // some stuff
}

After:

7Day() {    
    // some stuff
}

I quickly discovered that the javascript no longer worked. I heard from several people that numbers should never be used for method or class names. Is there ever an exception to this?

• javascript
• naming-conventions
• naming

Share Improve this question Follow edited Oct 2, 2020 at 12:15 m02ph3u5 3,16177 gold badges4141 silver badges5757 bronze badges asked Jan 22, 2009 at 21:52 Bobby BorszichBobby Borszich 11.8k99 gold badges4040 silver badges3535 bronze badges

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2 Answers 2

Sorted by: Reset to default 7

It tends to cause fits for language parsers. It sees a leading digit, so expects to begin reading a numeric literal, then barfs when it sees a letter. Even the algebraic convention is that a number to the left of a letter is a separate numeric literal with the space omitted, so 7x would be seen as two tokens.

Besides what Jeffrey Hantin said, there are numeric constants such as

3e7  // 3x10^7
40L  // C, C++, etc for a long integer
0x88 // hexadecimal

The general convention for identifiers which is used widely in most languages, is [S except for 0-9][S]* where S is some set of valid characters (A-Z, a-z, 0-9, sometimes _, $, or -) -- so the first character can't be a digit but the rest can.

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