Should not have unused variables JS-0128
Bug risk
Major
5 months ago
—
2 years old
'n' is defined but never used
11852 })),
11853 (l.escKey = t(document, "keyup", function () {
11854 var e = e || window.event,
11855 n = (function (e, n) {11856 return (
11857 "undefined" != typeof getComputedStyle
11858 ? getComputedStyle(e, null)'r' is defined but never used
10634 }),
10635 !M.dataType && M.target
10636 ? ((d = M.success || function () {}),
10637 h.push(function (e, t, r) {10638 var a = arguments,
10639 n = M.replaceTarget ? "replaceWith" : "html";
10640 q(M.target)'t' is defined but never used
10634 }),
10635 !M.dataType && M.target
10636 ? ((d = M.success || function () {}),
10637 h.push(function (e, t, r) {10638 var a = arguments,
10639 n = M.replaceTarget ? "replaceWith" : "html";
10640 q(M.target)'status' is defined but never used
9829 item.value = response.new;
9830 });
9831 },
9832 add_css: function add_css(ajax, response, status) { 9833 $("head").prepend(response.data);
9834 },
9835 message: function message(ajax, response) {'status' is defined but never used
9820 .filter(":odd")
9821 .addClass("even");
9822 },
9823 update_build_id: function update_build_id(ajax, response, status) { 9824 document
9825 .querySelectorAll(
9826 'input[name="form_build_id"][value="'.concat(response.old, '"]'),
Description
Found variables that are declared but not used anywhere.
NOTE: In browser applications, DeepSource recommends the use of ESModules over regular
text/javascriptscripts. Currently, we don't support variables that are not explicitly exported, and are injected into other scripts by being included in an HTML file
Unused variables are most often the result of incomplete refactoring. They can lead to confusing code and minor performance hitches.
NOTE: If you have intentionally left a variable unused, we suggest you to prefix the variable name with a _ to prevent them from being flagged by DeepSource.
Bad Practice
// Write-only variables are not considered as used.
let y = 10;
y = 5;
// A variable that modifies only itself isn't considered used.
let z = 0;
z = z + 1;
// Unused argument
(function(x) {
return 5;
})();
// Unused recursive functions also raise this issue.
function fact(n) {
if (n < 2) return 1;
return n * fact(n - 1);
}
// When a function definition destructures an array,
// unused entries from the array also cause warnings.
function getY([x, y]) {
return y;
}
Recommended
let x = 10;
alert(x);
((arg1) => {
return arg1;
})();
let myFunc;
myFunc = (n) => {
// this is legal
if (n < 0) myFunc();
};
// this is also considered legal
console.log(declaredLater);
var declaredLater;
// Only the second argument from the descructured array is used.
function getY([, y]) {
return y;
}