选项链接不适用于 array.length === x

Question

 let products; if (products?.length !== 0) { console.log('true') }

vs

 let products; if (products && products.length !== 0) { console.log('true') }

If there is no product array, example 1 will still run the if statement. Shouldn't the optional chaining check to see if product exists, then check for the length and finally check length to 0?

Example. 2 will not run if product does not exist.

Answer 1

Optional chaining does not take precedence over comparison. This

if (products?.length !== 0) {

is

if ((products?.length) !== 0) {

It evaluates the chain, then compares the result to 0. If there was a value at the end of the chain, that'll be compared. If the chain failed due to something being nullish, it'll evaluate to undefined , and that will be compared with 0.

if ((undefined) !== 0) {

which will always be true.

Since you want the block to run if products exists and isn't empty, use

if (products?.length) {