When is JavaScript\'s \'with\' Statement Legitimately Used?

Exploring Legitimate Uses for JavaScript's "with" Statement

When using the "with" statement, it's important to consider both its benefits and potential drawbacks. While it can be useful in certain scenarios, it's crucial to use it responsibly to avoid unexpected behavior.

One legitimate use of "with" is for defining variables inside block scope before ES6. JavaScript doesn't naturally scope variables to the block they're defined in, which can lead to issues when declaring closures within loops.

For example, the following code without the "with" statement will share the same "num" variable across multiple timeout functions:

for (var i = 0; i < 3; ++i) {
  var num = i;
  setTimeout(() => { alert(num); }, 10);
}

With the "with" statement, you can simulate the block scope needed to isolate the "num" variable for each timeout:

for (var i = 0; i < 3; ++i) {
  with ({num: i}) {
    setTimeout(() => { alert(num); }, 10);
  }
}

Note that this won't affect the scoping of variables declared within the block.

Another potential use of "with" is for code organization. Placing frequently accessed object members within the scope of a "with" block can make code easier to read and maintain. However, it's important to use this sparingly to avoid potential performance issues and unexpected behavior.

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