1.Use Boolean objects for conversion
Copy the codeThe code is as follows:
var num123 = 123, str = 'abc', o = {name:'test'}, num0 = 0; num123 = Boolean(num123); //true num0 = Boolean(num0); //false str = Boolean(str); //true o = Boolean(o); //true
2.Using two '!' operators, the first '!' converts the value into a boolean value and takes the non-value of its value, and the second '!' restores its boolean value, similar to the principle of "negative negative and positive".
Copy the codeThe code is as follows:
var num123 = 123, str = 'abc', o = {name:'test'}, num0 = 0; num123 = !!(num123); //true num0 = !!(num0); //false str = !!(str); //true o = !!(o); //true
The results obtained are the same as method 1.
Finally, you need to know: Any javascript value can be converted into a boolean value. The following values will be converted to false:
Copy the codeThe code is as follows:
undefined,null,0,-0,NaN,"" //Empty string
Need to pay attentionThe '0' string containing only 0 will be converted to true!
Add to the particularity of null and undefined:
Copy the codeThe code is as follows:
null == undefined //true null === undefined //false