JavaScript Symbol unscopables Property

JavaScript Symbol unscopables Property with examples on javascript symbol methods, javascript symbol property, javascript tutorial, hasInstance, isConcatSpreadable, match, prototype, search, for(), keyFor(), toString(), unscopables, toPrimitive, split etc.

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JavaScript Symbol.unscopables Properties

The Java Symbol.unscopables symbol is an object value whose inherited property names are excluded from with environment bindings.

NOTE:

Setting a property to true in an unscopables object makes it unscopable and therefore it won't appear in lexical scope variables.
Setting a property to false makes it scopable and thus it will appear in lexical scope variables.

Syntax

[Symbol.unscopables]

Parameters

Object.

Return value

Check the variable appear in lexical scope variable.

Browser Support

Chrome	32
Safari	8
Firefox	29
Opera	19

Example 1

//JavaScript to illustrate Symbol.toPrimitive
var obj = { 
  j: 1, 
  k: 2 
};
obj[Symbol.unscopables] = {  
//Setting a property to false will make it scopable 
  j: false,
//Setting a property to true in an unscopables object   
  k: true 
};
with (obj) {
  document.write(j);
}
//expected output: 1

Test it Now

Output:

Example 2

<script>
//JavaScript to illustrate Symbol.toPrimitive
var obj = { 
  j: "JavaTpoint", 
  k: "Core Java"
};
obj[Symbol.unscopables] = {  
//Setting a property to false will make it scopable 
  j: false,
//Setting a property to true in an unscopables object   
  k: true 
};
with (obj) {
  document.write(j);
}
//expected output: JavaTpoint
</script>

Test it Now

Output:

JavaTpoint

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