Detected the use of variables before they are defined JS-0357
Anti-pattern
Major
8 months ago
—
2 years old
'setSysMsg' was used before it was defined
45 dispath(setOnlineUsers(msg.users));
46 return;
47 }
48 setSysMsg(msg); 49 },
50 onOpen: () => {
51 const token = localStorage.getItem("token");'msgs' was used before it was defined
39 onMessage: ({ data }) => {
40 const msg = JSON.parse(data);
41 if (msg.type === "chat") {
42 setMsgs([...msgs, msg]); 43 return;
44 } else if (msg.type === "usersList") {
45 dispath(setOnlineUsers(msg.users));'setMsgs' was used before it was defined
39 onMessage: ({ data }) => {
40 const msg = JSON.parse(data);
41 if (msg.type === "chat") {
42 setMsgs([...msgs, msg]); 43 return;
44 } else if (msg.type === "usersList") {
45 dispath(setOnlineUsers(msg.users));'postId' was used before it was defined
39 observer.current = new IntersectionObserver(async (entries) => {
40 if (entries[0].isIntersecting && hasMore) {
41 await getComments({
42 postId: parseInt(postId as string), 43 lastId: lastId,
44 })
45 }'setSubmit' was used before it was defined
46 formData.append(`image${i + 1}`, productImages[i]);
47 }
48 await createProduct(formData);
49 setSubmit(false); 50 dispatch(setShowStep2(false));
51 setTimeout(
52 () =>
Description
Variables, functions and types should always be used after they've been defined. This issue will flag any code snippets that use variables or types before definition.
Sometimes, the code will run just fine even when the variable is declared after use. Consider the following example:
const ram: Resource = { type: "memory", limit: 1024 ** 3 }
type Resource = {
type: string;
limit: number;
}
Here, Resource is used in the annotation before it has been defined.
Similarly, it is possible to hoist function declarations and variables declared with the var keyword:
const four = twice(2);
function twice(n: number) {
return n * 2;
}
However, it makes the code harder to follow when variables or types are declared after being used.
Bad Practice
const knight: Radiant = {
order: "SurgeBinder"
strength: 30
}
interface Radiant {
order: string;
strength: number;
}
Recommended
interface Radiant {
order: string;
strength: number;
}
const knight: Radiant = {
order: "SurgeBinder"
strength: 30
}