I have a function that defines onlytest after the first execution of another script, but at the first run it was not defined.
How can I detect that it has not been set and give return; so the code stops? I've tried:
if(!onlytest) {
return;
}
but it does not work, it says it has not been defined, how to avoid this error and give the return when it is not defined?
The simplest way to check if the variable was defined takes into account that js considers the value undefined as false in a condition. However, the null and 0 values are also considered as false .
if (onlyteste) {
// existe
}
A more correct way, given that it only passes when the variable has not really been defined:
if (typeof onlyteste != 'undefined') {
// existe
}
Going even further, typescript generates the following code:
if (onlyteste !== void 0) {
// existe
}
Edit
A detail in your question that I did not realize when I compiled the answer: If the variable is not yet declared , only the second solution I submitted will work. Use any of the solutions (with the exception of the first) to check if the variable has been initialized / set.
function minhaFuncao () {
if (1 == 0) {
var onlyteste = 'ok';
}
if (typeof onlyteste == 'undefined') {
// variável não existe
}
}
function minhaFuncao () {
var onlyteste;
if (1 == 0) {
onlyteste = 'ok';
}
if (onlyteste) {
// não inicializada
}
if (typeof onlyteste == 'undefined') {
// não inicializada
}
if (onlyteste === void 0) {
// não inicializada
}
}
You can first check whether the variable has been defined. So:
if(onlytest !== undefined){
//Ações aqui
}
In this way, you can know whether or not the variable has been set. And here's something similar to what you wanted to do:
if(onlytest === undefined){
return false;
}