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rules.jshint.W056.html Maven / Gradle / Ivy

    
When do I get this error?
The "Bad constructor" error is thrown when JSLint or JSHint encounters the
new operator followed by a literal value. In the following example we are
attempting to apply the new operator to a numeric literal:
​x
 
1
var num = new 5();
2
​
JSLint found 1 error
Which linter should be used for this code snippet:
 JSLint JSHint ESLint
Which version of the linter should be used:
Update
Version 2015-09-23
Line 0:
Unexpected '('.

Why do I get this error?
In the case of assignment to a function call this error is raised to highlight a
fatal type error. Your code will throw an error in all environments if
you do not resolve this issue.
The new operator attempts to invoke the internal [[Construct]] property of
its operand (ES5 §11.2.2):

The production NewExpression : new NewExpression is evaluated as follows:



    1. Let ref be the result of evaluating NewExpression.


    2. Let constructor be GetValue(ref).

    3. If Type(constructor) is not Object, throw a
TypeError exception.

    4. If constructor does not implement the [[Construct]]
internal method, throw a TypeError exception.

We are particularly interested in steps 3 and 4. In the example above the
operand is a numeric literal and therefore its type is not "Object". As stated
by the third rule this will cause a type error to be thrown.
If the type of the operand is Object but it does not have an internal
[[Construct]] method the same thing happens and a type error is thrown in step

JSLint and JSHint can detect this to a point and will issue the same "Bad
constructor" warning if you attempt to apply new to an object literal:

2
 
1
var num = new {}();
2
​
JSLint found 2 errors
Which linter should be used for this code snippet:
 JSLint JSHint ESLint
Which version of the linter should be used:
Update
Version 2015-09-23
Line 0:
Unexpected space between 'new' and '{'.
Line 0:
Unexpected '('.

To avoid this warning simply stop attempting to misuse the new operator. It is
only useful for creating instances of a constructor function and has no sensible
meaning when applied to non-function objects or literals.
In JSHint 1.0.0 and above you have the ability to ignore any warning with a
special option syntax. The identifier of this warning is W056.
This means you can tell JSHint to not issue this warning with the /*jshint
-W056 */ directive.