Typescript call Object method from variable

Question

I have a node buffer

const meter = {
   readFunction: 'readUIntLE',
}
const buf = Buffer.from('01590D000022B65160010044BC1F000003036801', 'hex')
const method = meter.readFunction

I want to execute buf[method](0,1) but typescript warns me with an error

Element implicitly has an 'any' type because index expression is not of type 'number'

Eval doesn't look good to execute, but I am not too sure how to get rid or an error by other means

sorry revised code

iLyas
– iLyas

2021-04-02 05:46:26 +00:00
Commented Apr 2, 2021 at 5:46 — iLyas
– iLyas, Commented Apr 2, 2021 at 5:46

CertainPerformance · Accepted Answer · 2021-04-02 05:48:30Z

2

The problem is that your object is typed as

readFunction: string

and not

readFunction: 'readUIntLE'

so TS doesn't see that the buf[method] refers to the method you want - it just sees an arbitrary string, which could be anything.

Declare the object as const to avoid the problematic widening.

const meter = {
    readFunction: 'readUIntLE' as const,
}

answered Apr 2, 2021 at 5:48

CertainPerformance

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CertainPerformance Over a year ago

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