Tuesday, 4 April, 2023 UTC
Summary
The Javascript
1. No other code is allowed the label declaration and its loop
uncaught SyntaxError: Undefined label <<label name here>> might happen because one of the following reasons.The label name needs to come right after its corresponding loop. No other code is allowed between the label declaration and its loop:
// ⛔️ this will throw:
// uncaught SyntaxError: Undefined label myLabel
myLabel:
console.log('something)
for (let i = 0; i < 5; i++) { ... }
// ✅ this will work
myLabel:
for (let i = 0; i < 5; i++) { ... }The label must be declared BEFORE using it with a break or a continue statement:
// ⛔️ this will throw:
// uncaught SyntaxError: Undefined label myLabel
for (let i = 0; i < 5; i++) {
if(i === 1) break myLabel;
}
myLabel:
// ✅ this will work
myLabel:
for (let i = 0; i < 5; i++) {
if(i === 1) break myLabel;
}Javascript labels are not meant to work as a goto statement and can be used only with prior defined simple or nested loops.
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