How to check if array is empty using if condition?

Question

respons is coming back empty [] for this.rxInfos but below if condtion never executed any idea what is missing here ?

main.js

if (!Array.isArray(this.rxInfos) && this.rxInfos.length === 0) {
            return this.errorHandler(request, 'no rx found in the cache');
        }

Using &&, you are checking that both are true at the same time. — Alfabravo
– Alfabravo, Commented Jan 4, 2019 at 17:19
read it out loud: if (not an Array AND the length is zero) — epascarello
– epascarello, Commented Jan 4, 2019 at 17:21

Nina Scholz · Accepted Answer · 2019-01-04 17:55:53Z

2

You could check not an array or if no length.

The first part

!Array.isArray(this.rxInfos)

is true, if the value of this.rxInfos is not an array.

The logical OR || allows to end the check, which is important, if the first operand it truthy. If not, then an array is given and the second part

!this.rxInfos.length

with the length and their logical NOT ! is evaluated and that means, if a length of zero, the last part is true or if the length has another value than zero, the part yields false.

if (!Array.isArray(this.rxInfos) || !this.rxInfos.length) {
    return this.errorHandler(request, 'no rx found in the cache');
}

edited Jan 4, 2019 at 17:55

answered Jan 4, 2019 at 17:21

Nina Scholz

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1 Comment

Marie Over a year ago

The solution was to use || not &&, you made the change but didnt really explain why you made the change. Your length check and theirs accomplish the same thing so it is really inconsequential.

NaDeR Star · Accepted Answer · 2019-01-04 17:40:33Z

0

Just remove first !

 if (this.rxInfos !== undefined && Array.isArray(this.rxInfos) && this.rxInfos.length === 0) { return this.errorHandler(request, 'no rx found in the cache'); }

edited Jan 4, 2019 at 17:40

answered Jan 4, 2019 at 17:23

NaDeR Star

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