Underscore.js _.isError() Function

Last Updated : 25 Nov, 2021

Underscore.js is a library in javascript that makes operations on arrays, string, objects much easier and handy. _.isError() function is used to check whether the given object is javascript Error Object or not.

Note: It is very necessary to link the underscore CDN before going and using underscore functions in the browser. When linking the underscore.js CDN The "_" is attached to the browser as a global variable.

Syntax:

_.isError(object);

Parameters: It takes only one parameter i.e object.

Returns: It returns the boolean value. If the object is a inherit from Error object of javascript it returns true otherwise false is returned by the function.

Few Examples are given below for a better understanding of the function.

Example 1: When error is created from error object

html

<!DOCTYPE html> 
<html> 
  <head> 
    <script src =  
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js" > 
    </script> 
   </head> 
  <body>
    <script>
      let e=new Error()
      let ans=_.isError(e)
      console.log(_.isError(e))
      if(ans)
      console.log("It is the javascript error")
    </script>
  </body> 
</html>

Output:

Example 2: When try catch is used to throw error.

html

<!DOCTYPE html> 
<html> 
  <head> 
    <script src =  
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js" > 
    </script> 
   </head> 
  <body>
    <script>
      let e;
      try{
        alrt("GeeksforGeeks")
      }
      catch(e){
        let ans=_.isError(e)
        console.log(`Error is ${e}`)
        console.log(_.isError(e))
        if(ans)
        console.log("It is the javascript error object")
      }
    </script>
  </body> 
</html>

Output:

Example 3: When given error is string type.

html

<!DOCTYPE html> 
<html> 
  <head> 
    <script src =  
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js" > 
    </script> 
   </head> 
  <body>
    <script>
      let e="some error"
      let ans=_.isError(e)
      console.log(_.isError(e))
      if(ans)
      console.log("It is the javascript error object")
      else
      console.log("It is not the javascript error object")
    </script>
  </body> 
</html>