10. Else,<\/p>\n
a. Let lexEnv be NewDeclarativeEnvironment(evalRealm.[[GlobalEnv]]).
\n
b. Let varEnv be evalRealm.[[GlobalEnv]].\n<\/p><\/blockquote>\n<\/blockquote>\n
So for an indirect call (not calling eval<\/code><\/strong> by name) you arrive at step 10 which calls NewDeclarativeEnvironment(E)<\/code> with the global environment record as parameter value.<\/p>\nNewDeclarativeEnvironment<\/code> is described in section 8.1.2.2. As expected this creates an environment record for any variables defined using let<\/code> within script parsed by eval<\/code>, and sets the “outer lexical environment reference<\/strong>” of that record to the environment record provided as argument.<\/p>\nStep 10.b sets the variable environment record, for named functions and variables declared with var<\/code>, to the global environment record of the realm eval<\/code> was called in \u2013 meaning window<\/code> in a browser document.<\/p>\nIn short, calling eval<\/code> indirectly creates a separate environment record for let<\/code> variables declared within the code being evaluated, whose next outer scope (lexical reference) is the global object, but uses the global object for var<\/code> and named function declarations. <\/p>\nIf you want to have evaluated code inherit the scope of surrounding code, make a direct call using the name eval<\/code> as the function reference.<\/p>\nThe presence of both 9.a and 10.a means that variables declared with let<\/code> are not retained after a call to eval<\/code> no matter what the type of call.. <\/p>\n<\/p>\n
\nThe Historical Why<\/strong> (edit)<\/p>\nThe behavior of indirect calls is likely the result of deprecating calling eval<\/code> on an object and removing the eval<\/code> property from Object.prototype<\/code>.<\/p>\nFrom the JavaScript 1.2 reference for Object data type methods:<\/p>\n
\neval \u00a0 \u00a0 \u00a0 Evaluates a string of JavaScript code in the context of the specified object.<\/p>\n<\/blockquote>\n
and calling eval<\/code> on an object in such early versions of JavaScript would result in code evaluation as if it were inside a with (object) {}<\/code> statement.<\/p>\nThe rules for indirect calls replace this behavior with a standard response: if an object method is set to eval<\/code> the previous behavior of object.eval<\/code> is not recreated and the scope of evaluated code is the global object exceot for let<\/code> variables. This is similar to the way creating a function from text with new Function<\/code> behaves as if it were defined in global scope. It also has the effect that the this<\/code> value seen by indirect calls to eval<\/code> is the global object (this<\/code> values reside in environmental records).<\/p>\n<\/p><\/div>\n<\/div>\n<\/div>\n
<\/span> <\/p><\/div>\n<\/div>\n[ad_2]<\/p>\n
solved Javascript scoping change <\/p>\n","protected":false},"excerpt":{"rendered":"
[ad_1] The following excerpts are taken from ECMA-262 7th edition (ECMAScript 2016) \u2013 section numbers sometimes differ between versions. 18.2.1.1 Runtime Semantics: PerformEval( x, evalRealm, strictCaller, direct) … 9. If direct is true, then a. Let lexEnv be NewDeclarativeEnvironment(ctx’s LexicalEnvironment). b. Let varEnv be ctx’s VariableEnvironment. 10. Else, a. Let lexEnv be NewDeclarativeEnvironment(evalRealm.[[GlobalEnv]]). b. Let … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[333],"class_list":["post-8309","post","type-post","status-publish","format-standard","hentry","category-solved","tag-javascript"],"yoast_head":"\n[Solved] Javascript scoping change - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-javascript-scoping-change\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Javascript scoping change - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] The following excerpts are taken from ECMA-262 7th edition (ECMAScript 2016) \u2013 section numbers sometimes differ between versions. 18.2.1.1 Runtime Semantics: PerformEval( x, evalRealm, strictCaller, direct) … 9. If direct is true, then a. Let lexEnv be NewDeclarativeEnvironment(ctx’s LexicalEnvironment). b. Let varEnv be ctx’s VariableEnvironment. 10. Else, a. Let lexEnv be NewDeclarativeEnvironment(evalRealm.[[GlobalEnv]]). b. Let ... 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