Question 264871 in Javascript Question posted in
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Javascript – Execution of Assigning value and Logical AND and Ternary operator

I am learning JavaScript, and I do not understand what is the execution sequence of 2nd line. Please advise!

let envArr;
const envName = envArr && envArr[0] ? envArr[0] : "env1";
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2

Answers


  1. 0

    1.envArr && envArr[0]
    2. true:envArr[0]
    false:"env1"

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  2. 0

    Here output of envArr && envArr[0] would be considered for execution of ternary operator.

    On other hand doing something like this (it’s illogical, but just for sake of example) –

    envArr && (envArr[0] ? envArr[0] : "env1");

    Will execute ternary operation based on solely envArr[0] and it’s output will be anded with envArr, simplified version will look like this.

    envArr && output_of_ternary

    BTW better way of doing above check from your question will be like this –

    const envName = envArr?.[0] || 'env1'

    We are using optional chaining, you can find more details about optional chaining here

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