Typescript does not recognize function Boolean() as a check for undefined
#24,063 opened on May 11, 2018
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Description
I followed the submission guidelines.
I prefer to check for a defined object using Boolean(object) rather than !!object, which I consider bad style. Typescript linter recognizes !! as a check for undefined but does not recognize Boolean() as a check for undefined.
I could not find a tsconfig or tslint configuration setting related to this behavior.
2.9.0-dev.20180511 (typescript@next)
"Boolean" "Boolean(" "function Boolean"
Code This is not production code but a simple demonstration only to satisfy the expression tree.
function booleanTest() {
let value: Array<object> | undefined = undefined;
if (Date.now() > 1) {
value = [{}];
}
if (Boolean(value)) {
console.log(value.length);
}
}
Expected behavior: No Typescript linter errors
Actual behavior: Typescript linter in VS Code displays an error "[ts] Object is possibly 'undefined'." with a red squiggly on the final reference to variable "value".
Playground Link: