CODEWITHSUNDEEP
javascriptwith-statementscope-chain
Piotrek Hryciuk
Piotrek Hryciuk

Reputation: 795

To which variable object statements inside with are bind?

function buildUrl() {
  var qs = "?debug=true";
  with(location){
    var url = href + qs;
  }
  return url;
}
buildUrl(); // it will work. WHY?

I am working through a "Professional JavaScript for Web Developers" by N. Zakas, and I came across this snippet. From my understanding with is a statement that augments scope chain by pushing, in this case, location object to the front.

It seems that url local variable is assigned to a function activation object. Why isn't it assigned to location?

Upvotes: 1

Views: 62

Answers (2)

Bardy
Bardy

Reputation: 2170

with adds the argument location for the purposes of lookup, but your var url is still hoisted to the containing function - i.e. buildUrl as you are creating a variable, not looking one up.

However, you should completely avoid with, see the statement on MDN.

Upvotes: 1

locropulenton
locropulenton

Reputation: 4853

The with statement is deprecated

The use of the with statement is generally discouraged. It is forbidden in strict mode:

function foo() { "use strict"; with({}); }

SyntaxError: strict mode code may not contain 'with' statements Best practice: Don’t use a with statement.

with(foo.bar.baz) {
    console.log("Hello "+first+" "+last);
}

Do use a temporary variable with a short name.

var b = foo.bar.baz; 
console.log("Hello "+b.first+" "+b.last);

Upvotes: 0

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