Episode 010

[ahJ4s|1724220152149|Tue Aug 20 2024 23:02:32 GMT-0700 (Pacific Daylight Time)|code]

"This 'with' was an early JavaScript feature";
(function(){

var return_value;
var scope;

scope =
  {
    foo: 42
  };
with (scope)
  return_value = foo;
return return_value;

})();

[ahJ4s|1724220152158|Tue Aug 20 2024 23:02:32 GMT-0700 (Pacific Daylight Time)|value]

42

[ahJ4s|1724220212823|Tue Aug 20 2024 23:03:32 GMT-0700 (Pacific Daylight Time)|code]

"Some people do not like 'with' and some people invented strict mode";
(function(){
"use strict";

var return_value;
var scope;

scope =
  {
    foo: 42
  };
with (scope)
  return_value = foo;
return return_value;

})();

[ahJ4s|1724220212825|Tue Aug 20 2024 23:03:32 GMT-0700 (Pacific Daylight Time)|error]

SyntaxError: Strict mode code may not include a with statement
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220288427|Tue Aug 20 2024 23:04:48 GMT-0700 (Pacific Daylight Time)|code]

"An anonymous function via the Function constructor";
function_via_constructor = Function("return typeof anonymous;");
"OK";

[ahJ4s|1724220288429|Tue Aug 20 2024 23:04:48 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1724220298221|Tue Aug 20 2024 23:04:58 GMT-0700 (Pacific Daylight Time)|code]

"The string representation";
function_via_constructor.toString();

[ahJ4s|1724220298223|Tue Aug 20 2024 23:04:58 GMT-0700 (Pacific Daylight Time)|value]

function anonymous(
) {
return typeof anonymous;
}

[ahJ4s|1724220333618|Tue Aug 20 2024 23:05:33 GMT-0700 (Pacific Daylight Time)|code]

"Despite the name, the identifier does not pollute the scope";
function_via_constructor();

[ahJ4s|1724220333619|Tue Aug 20 2024 23:05:33 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1724220380602|Tue Aug 20 2024 23:06:20 GMT-0700 (Pacific Daylight Time)|code]

"With named parameters";
function_via_constructor2 = Function("one", "two", "return typeof two;");

[ahJ4s|1724220380603|Tue Aug 20 2024 23:06:20 GMT-0700 (Pacific Daylight Time)|value]

function anonymous(one,two
) {
return typeof two;
}

[ahJ4s|1724220413125|Tue Aug 20 2024 23:06:53 GMT-0700 (Pacific Daylight Time)|code]

"Named parameters are in the scope";
function_via_constructor2("answer", 42);

[ahJ4s|1724220413125|Tue Aug 20 2024 23:06:53 GMT-0700 (Pacific Daylight Time)|value]

number

[ahJ4s|1724220424973|Tue Aug 20 2024 23:07:04 GMT-0700 (Pacific Daylight Time)|code]

"Today's special";
ep010 = (function(){

var bar;

bar = 42;

return {
    rescope: rescope,
    scope_check: scope_check
  };

function rescope(func, new_scope)
  {
    var builder;
    var builder_parts;
    var constructor_parts;
    var func_string;
    var i;
    var key;
    var new_func;
    var noted;
    var object_keys;

    if (arguments.length > 2)
      throw new Error("rescope: takes a maximum of 2 arguments");
    if (arguments.length == 0)
      {
        if (typeof this != "function")
          throw new Error("rescope: 'this' must be a function, for 0 arguments");
        return rescope(this);
      }
    if (arguments.length == 1)
      {
        if (typeof func == "function")
          return rescope(func, undefined);
        if (typeof this != "function")
          throw new Error("rescope: must involve a function, for 1 argument");
        return rescope(this, func);
      }
    if (typeof func != "function")
      throw new Error("rescope: func must be a function");
    builder_parts = [];
    constructor_parts = [];
    func_string = func.toString();
    if (arguments.length == 2 && typeof new_scope != "undefined" && new_scope !== null)
      {
        if (typeof new_scope != "object")
          throw new Error("rescope: new scope must be an object, if specified");
        noted = {};
        if (typeof Object.keys == "function")
          {
            object_keys = Object.keys(new_scope);
            for (i = 0; i < object_keys.length; ++i)
              {
                key = object_keys[i];
                if (noted[key] === noted)
                  continue;
                builder_parts.push(new_scope[key]);
                constructor_parts.push(key);
                noted[key] = noted;
              }
          }
        for (key in new_scope)
          {
            if (noted[key] === noted)
              continue;
            builder_parts.push(new_scope[key]);
            constructor_parts.push(key);
            noted[key] = noted;
          }
        noted = null;
      }
    constructor_parts.push("return " + func_string + ";");
    builder = Function.apply(null, constructor_parts);
    new_func = builder.apply(null, builder_parts);
    return new_func;
  }

function scope_check(code)
  {
    return eval(code);
  }

})();

[ahJ4s|1724220424974|Tue Aug 20 2024 23:07:04 GMT-0700 (Pacific Daylight Time)|value]

[object Object]

[ahJ4s|1724220865619|Tue Aug 20 2024 23:14:25 GMT-0700 (Pacific Daylight Time)|code]

"scope_check has bar in scope";
ep010.scope_check("typeof bar");

[ahJ4s|1724220865622|Tue Aug 20 2024 23:14:25 GMT-0700 (Pacific Daylight Time)|value]

number

[ahJ4s|1724220874380|Tue Aug 20 2024 23:14:34 GMT-0700 (Pacific Daylight Time)|code]

"Obviously the value, too";
ep010.scope_check("bar");

[ahJ4s|1724220874381|Tue Aug 20 2024 23:14:34 GMT-0700 (Pacific Daylight Time)|value]

42

[ahJ4s|1724220885905|Tue Aug 20 2024 23:14:45 GMT-0700 (Pacific Daylight Time)|code]

"Too many arguments";
ep010.rescope(1, 2, 3);

[ahJ4s|1724220885910|Tue Aug 20 2024 23:14:45 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: takes a maximum of 2 arguments
    at Object.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:26:13)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:7)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220896586|Tue Aug 20 2024 23:14:56 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, no arguments";
ep010.rescope();

[ahJ4s|1724220896587|Tue Aug 20 2024 23:14:56 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: 'this' must be a function, for 0 arguments
    at Object.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:30:17)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:7)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220903219|Tue Aug 20 2024 23:15:03 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, non-function argument";
ep010.rescope(1);

[ahJ4s|1724220903220|Tue Aug 20 2024 23:15:03 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: must involve a function, for 1 argument
    at Object.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:38:17)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:7)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220911057|Tue Aug 20 2024 23:15:11 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, non-function first argument, two arguments";
ep010.rescope(1, 2);

[ahJ4s|1724220911058|Tue Aug 20 2024 23:15:11 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: func must be a function
    at Object.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:42:13)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:7)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220922845|Tue Aug 20 2024 23:15:22 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, function as first argument, non-object as second argument";
ep010.rescope(function(){}, 2);

[ahJ4s|1724220922846|Tue Aug 20 2024 23:15:22 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: new scope must be an object, if specified
    at Object.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:49:17)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:7)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220949581|Tue Aug 20 2024 23:15:49 GMT-0700 (Pacific Daylight Time)|code]

"Add rescope as property of scope_check.  Could go into Function.prototype";
ep010.scope_check.rescope = ep010.rescope;
"OK";

[ahJ4s|1724220949581|Tue Aug 20 2024 23:15:49 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1724220957578|Tue Aug 20 2024 23:15:57 GMT-0700 (Pacific Daylight Time)|code]

"Function this, non-object argument";
ep010.scope_check.rescope(42);

[ahJ4s|1724220957580|Tue Aug 20 2024 23:15:57 GMT-0700 (Pacific Daylight Time)|error]

Error: rescope: new scope must be an object, if specified
    at rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:49:17)
    at Function.rescope (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:39:16)
    at eval (eval at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:1:2184), <anonymous>:2:19)
    at eval (<anonymous>)
    at safeEvaluate (https://www.sha0.net/codewhile/codewhile010.html:22:4860)
    at Object.execute (https://www.sha0.net/codewhile/codewhile010.html:22:3060)
    at https://www.sha0.net/codewhile/codewhile010.html:22:4936
    at HTMLButtonElement.onclick (https://www.sha0.net/codewhile/codewhile010.html:22:4949)

[ahJ4s|1724220977623|Tue Aug 20 2024 23:16:17 GMT-0700 (Pacific Daylight Time)|code]

"A new scope_check with a fresh scope";
ep010.scope_check2 = ep010.scope_check.rescope();
"OK";

[ahJ4s|1724220977632|Tue Aug 20 2024 23:16:17 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1724220989561|Tue Aug 20 2024 23:16:29 GMT-0700 (Pacific Daylight Time)|code]

"String representations should be equivalent";
(
  ep010.scope_check.toString()
  ===
  ep010.scope_check2.toString()
);

[ahJ4s|1724220989562|Tue Aug 20 2024 23:16:29 GMT-0700 (Pacific Daylight Time)|value]

true

[ahJ4s|1724221000845|Tue Aug 20 2024 23:16:40 GMT-0700 (Pacific Daylight Time)|code]

"They are not the same function, however";
(
  ep010.scope_check
  ===
  ep010.scope_check2
);

[ahJ4s|1724221000846|Tue Aug 20 2024 23:16:40 GMT-0700 (Pacific Daylight Time)|value]

false

[ahJ4s|1724221023860|Tue Aug 20 2024 23:17:03 GMT-0700 (Pacific Daylight Time)|code]

"The fresh scope means bar is not present";
ep010.scope_check2("typeof bar");

[ahJ4s|1724221023862|Tue Aug 20 2024 23:17:03 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1724221037233|Tue Aug 20 2024 23:17:17 GMT-0700 (Pacific Daylight Time)|code]

"Another scope_check with a specific scope";
ep010.scope_check3 = ep010.scope_check.rescope({ baz: 42 });

[ahJ4s|1724221037236|Tue Aug 20 2024 23:17:17 GMT-0700 (Pacific Daylight Time)|value]

function scope_check(code)
  {
    return eval(code);
  }

[ahJ4s|1724221053160|Tue Aug 20 2024 23:17:33 GMT-0700 (Pacific Daylight Time)|code]

"The specific scope has no bar";
ep010.scope_check3("typeof bar");

[ahJ4s|1724221053160|Tue Aug 20 2024 23:17:33 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1724221064349|Tue Aug 20 2024 23:17:44 GMT-0700 (Pacific Daylight Time)|code]

"But it has baz";
ep010.scope_check3("baz");

[ahJ4s|1724221064349|Tue Aug 20 2024 23:17:44 GMT-0700 (Pacific Daylight Time)|value]

42

[ahJ4s|1724221122431|Tue Aug 20 2024 23:18:42 GMT-0700 (Pacific Daylight Time)|code]

"MSIE6 returns false";
ep010.scope_check3("ep010.scope_check3 === scope_check");

[ahJ4s|1724221122432|Tue Aug 20 2024 23:18:42 GMT-0700 (Pacific Daylight Time)|value]

true

[ahJ4s|1724221167417|Tue Aug 20 2024 23:19:27 GMT-0700 (Pacific Daylight Time)|code]

"Seeking truth with MSIE6";
ep010.scope_check3("ep010.scope_check4 = scope_check");
ep010.scope_check4("ep010.scope_check4 === scope_check");

[ahJ4s|1724221167417|Tue Aug 20 2024 23:19:27 GMT-0700 (Pacific Daylight Time)|value]

true

[ahJ4s|1724221186776|Tue Aug 20 2024 23:19:46 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, function argument";
ep010.scope_check5 = ep010.rescope(ep010.scope_check);

[ahJ4s|1724221186778|Tue Aug 20 2024 23:19:46 GMT-0700 (Pacific Daylight Time)|value]

function scope_check(code)
  {
    return eval(code);
  }

[ahJ4s|1724221200019|Tue Aug 20 2024 23:20:00 GMT-0700 (Pacific Daylight Time)|code]

"Non-function this, function argument, specific scope";
ep010.scope_check6 = ep010.rescope(ep010.scope_check, { qux: 42 });

[ahJ4s|1724221200020|Tue Aug 20 2024 23:20:00 GMT-0700 (Pacific Daylight Time)|value]

function scope_check(code)
  {
    return eval(code);
  }

[ahJ4s|1724221208645|Tue Aug 20 2024 23:20:08 GMT-0700 (Pacific Daylight Time)|code]

"Has qux";
ep010.scope_check6("qux");

[ahJ4s|1724221208645|Tue Aug 20 2024 23:20:08 GMT-0700 (Pacific Daylight Time)|value]

42

[ahJ4s|1724221213778|Tue Aug 20 2024 23:20:13 GMT-0700 (Pacific Daylight Time)|code]

"Not a replacement for the 'with' feature, due to value-copying, twice";
(function(){

var return_value;
var scope;

scope =
  {
    foo: 42,
    return_value: return_value
  };
ep010.rescope(with_scope, scope)();
function with_scope()
  {
    /* Assignment to a different return_value */
    return_value = foo;
  }
return return_value;

})();

[ahJ4s|1724221213780|Tue Aug 20 2024 23:20:13 GMT-0700 (Pacific Daylight Time)|value]

undefined