falsey var在console.log中显示未定义

Question

 var statusDatesDescending = ko.computed(function () { var result = cachedSortExpression() === "StringValue"; logger.log(result); return result; }); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script> <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 

The following provides this in the console when result is false:

logger.log("DESCENDING: ", result); DESCENDING: undefined

The following provides this in the console when result is true:

logger.log("DESCENDING: ", result); DESCENDING: true

Answer 1

What you might seeing is the return from console.log , as seen here, if you are using an interactive console.

Notice how false is logged before undefined . The console.log call executes, logging to the console, and then returns undefined. The return value of the call is shown because the interactive console always shows the result of any functions you enter into it.