JavaScript ReferenceError - Can't access lexical declaration`variable' before initialization
Last Updated :
05 Jun, 2023
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This JavaScript exception can't access the lexical declaration `variable' before initialization occurs if a lexical variable has been accessed before initialization. This could happen inside any block statement when let or const declarations are accessed when they are undefined.
Message:
ReferenceError: Use before declaration (Edge)
ReferenceError: can't access lexical declaration `variable' before
initialization (Firefox)
ReferenceError: 'variable' is not defined (Chrome)
Error Type:
ReferenceError
Cause of the error: Somewhere in the code, there is a lexical variable that was accessed before initialization.
Example 1: In this example, the const keyword is used with the variable inside the if statement, So the error has occurred.
function GFG() {
const var_1 = "This is";
if (true) {
const var_1 = var_1 + "GeeksforGeeks";
}
}
function Geeks() {
try {
GFG();
console.log(
"'Can't access lexical declaration" +
"`variable'before initialization' " +
"error has not occurred");
} catch (e) {
console.log(
"'Can't access lexical declaration" +
"`variable' before initialization'" +
" error has occurred");
}
}
Geeks()
Output
'Can't access lexical declaration`variable' before initialization' error has occurred
Example 2: In this example, the keyword is used with the variable, So the error has occurred.
function GFG() {
let var_1 = 3;
if (true) {
var_1 = var_1 + 5;
}
}
function Geeks() {
try {
GFG();
console.log(
"'Can't access lexical declaration" +
"`variable' before initialization'" +
" error has not occurred");
} catch (e) {
console.log(
"'Can't access lexical declaration" +
"`variable'before initialization'" +
" error has occurred");
}
}
Geeks()
Output
'Can't access lexical declaration`variable' before initialization' error has not occurred
