Javascript best practice-check whether a variable exists

In Javascript, the common way to check whether a variable exists is if (variable ){.... // variable exists} else {.... // variable does not exist}. When variable is undefined | null, that is, the variable does not exist. However, if variable is 0, this code will run... syntaxHighli

In Javascript, the common way to check whether a variable exists is

If (variable ){
... // Variable exists
} Else {
... // The variable does not exist
}
In this way, when variable is undefined | null, that is, the variable does not exist, but if variable is 0, this code will also fail to run, which is incorrect.

The perfect solution is as follows:

If (typeof variable! = "Undefined" & variable! = Null ){
....
}