1. "||" logical OR
Logic or " True truth ", the first one is true or not, the second one is true or not, until the true value is returned, if there is no true value at the end of the comparison, then there is no way to return the last value
one example:
{} Behind to protect the bottom , there is a real guarantee can spit
var data = res.data || {};
2. "&&" logical and
The logical AND is " fuse ". The first one is continuously broken, and the second one is continuous. The comparison is continued until it is broken. If none is broken, the comparison is at the end and the last value is displayed.
one example:
It can replace if for fusing. If the first one is broken, the values after it will not be executed and return false. If the first value is constant, the content after && will be assigned.
>var str = "123"
>var test = str.length > 0 && "zym";
console.log(`
---------test && -------
${
test}
`);
Output result:
---------test && -------
zym