Three ways to mutual exclusion in NodeJS

SharedPromise.ts

const wait = (s: number) => new Promise((resolve) => setTimeout(resolve, s * 1000))

let promRef

const download = async () => {
    if (promRef) return promRef

    promRef = wait(3).then(() => {
        console.log('finished')
        promRef = null
        return 'resolved'
    })
    return promRef
}

setInterval(() => download().then((r) => console.log(`${r} interval 1`)), 1 * 1000)
setInterval(() => download().then((r) => console.log(`${r} interval 2`)), 1 * 1000)
setInterval(() => download().then((r) => console.log(`${r} interval 3`)), 1 * 1000)

/*
Output:
[LOG]: "finished" 
[LOG]: "resolved interval 1" 
[LOG]: "resolved interval 2" 
[LOG]: "resolved interval 3" 
[LOG]: "resolved interval 1" 
[LOG]: "resolved interval 2" 
[LOG]: "resolved interval 3" 
[LOG]: "resolved interval 1" 
[LOG]: "resolved interval 2" 
[LOG]: "resolved interval 3" 
[LOG]: "resolved interval 1" 
[LOG]: "resolved interval 2" 
[LOG]: "resolved interval 3" 

Playground Link:https://www.typescriptlang.org/play?#code/MYewdgzgLgBA7gQwJawLwwBQQFwzAVwFsAjAUwCcBKGVAPj1LhgAVyRCkJSMNzSIQAGwBupanRhcoAFSSFSIfFF78hogDSSYAKhgBGAAxHKlALAAoC4NKwADm0IAlUgDMLF0JFgATEHDCCIAjeNDAIEACeYMCY4vQA3hYwyTBILpj27M4u1HxQ+ORgMJlOru7mKcUO2aGIKBgAzJQAdFAAFqRgPHEwiRWVKZ4C1s2BAOYYAOQuSGCcHd6TZv0DVVmuoQSCgkmrMHkFRZN8w6KLu8kAvsuVB4VrpW7ml+VSAJJgUBTCCILdNPRfP5AsEMC12p0eFQATAhkJSKMQBMAAYAEni5EuqU+31++mRJk0eh0+iMBmW7xx5B+fzBMKBASC3jBrQ6XV4PThI3GGDRGKxsy+1LxACYCZQiSTDMYLJShTT-hIGSDmeC2VDOeBhgieXzMdj5XiGuLJbppeSLEA

*/