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HTTP/2 200 date: Sun, 26 Jul 2026 03:12:51 GMT content-type: text/html server: nginx vary: Accept-Encoding x-frame-options: SAMEORIGIN strict-transport-security: max-age=31536000 content-encoding: gzip strict???[?h?Ƃ́H?mJavaScript?n?F.NET TIPS - ??IT

strict???[?h?Ƃ́H?mJavaScript?n?F.NET TIPS

???S??JavaScript?R?[?h?????????strict???[?h?͂??Ўg???????@?\?????A???Ƃ?????????B?{?e?ł?strict???[?h?̎g?????ƒ??ӓ_???Љ??B

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?@JavaScript???????Ă???Ƃ??A???????薢??`?̕ϐ????g???Ă??܂?????A?ϐ????̃X?y???~?X?????Ă??܂??āA?o?O???o???Ă??܂??????Ƃ͂Ȃ????낤???H ????Ȃ??Ƃ?h???ł????̂?strict???[?h?i???i???[?h?j???B?{?e?ł́A???̎g?????ƁA??̒??ӎ????????????B

strict???[?h?̐錾?ƌ???

?@?u"use strict";?v?i?܂??́u'use strict';?v?j?Ƃ???1????u?????ƂŁAstrict???[?h?ɂȂ?B

?@?X?N???v?g?̐擪?Ő錾????΁A?X?N???v?g?S?̂?strict???[?h?ɂȂ?B?֐??̐擪?Ő錾????΁A???̊֐?????????strict???[?h?ɂȂ?B????ȊO?̏ꏊ?Ő錾???Ă????ʂ͂Ȃ??̂Œ??ӂ??悤?B

?@?֐??X?R?[?v??strict???[?h???g??????A???̃R?[?h?Ɏ????B

// strict???[?h???g??Ȃ???
(function () {
x = 10; // ???[?J???ϐ??̂???ŏ??????ϐ??i?擪??var???????Y??j
var w = 15; // ????w?͐????????[?J???ϐ?
test(); // x=20, w=15
}());

// ??̊֐?????x?̓O???[?o???X?R?[?v?ɂȂ?̂ŁA?ǂ?????ł??ύX?ł???
function test() {
x = 20;
w = 25; // ????w?́A?O???[?o???X?R?[?v?̐V?????ϐ??ɂȂ?
}

// strict???[?h???g????
(function () {
"use strict";

// ????`?ϐ??̓G???[?ɂȂ?
try {
    y = 20;
}
catch (e) {
    alert(e);
    // Edge?ł̃G???[???b?Z?[?W
    // ReferenceError: Variable undefined in strict mode
}
}());

strict???[?h?̗?iJavaScript?j
?֐??̐擪?Ɂu"use strict";?v?Ə??????ƂŁA???̊֐?????strict???[?h?ɂȂ?B?֐??̓r???ɏ????Ă??L???ɂȂ?Ȃ??̂Œ??ӂ??悤?B
??strict???[?h?ł́A?ϐ??錾?????Ȃ??܂ܕϐ????g???ƁA?O???[?o???X?R?[?v?ŕϐ????錾???ꂽ???̂ƌ??Ȃ????B???̂??߁A???̗?̕ϐ??ux?v?̂悤?ɁA?֐????????Ŏg???Ă??????ł??O???[?o???X?R?[?v?ɂȂ??Ă??܂??Bstrict???[?h?ł́A?擪??var?L?[???[?h??t???ĕϐ???錾???Ȃ??ƃG???[?ɂȂ?̂ŁA???̂悤?ȃ~?X?͂Ȃ??Ȃ?B
?Ȃ??A???́u(function () {?c?c?ȗ??c?c}());?v?Ƃ????֐??̏??????͑????֐??iIIFE?AImmediately-invoked function expression?j?Ƃ??????̂??B?????֐??????̏?Ŏ??s???Ă????̂ł???B

?@strict???[?h?ł͏?̗?̂悤??var?L?[???[?h?̕t???Y???h???ł????B???̑??ɁA?ύX?ł??Ȃ??v???p?e?B?ւ̑????A?֐??̈??????̏d???i?Ⴆ?΁A2?̈????????֐??ŁA?????̉????????𓯂????O?Ő錾???邱?Ɓj?Ȃǂ??`?F?b?N?????B?ڍׂ́AMSDN??MDN?̃h?L???????g???????????????????B

?@???̂悤?ȃ????b?g?̂???strict???[?h?́A???ǂ???JavaScript?ł͎g???̂???????O???Ƃ????邾?낤?B???????A?g?p?ɓ??????ċC??t???邱?Ƃ?2?_????̂ŁA?ȍ~?Ő???????B

?X?N???v?g?A?????

?@??̗?ł͊֐?????strict???[?h??錾?????B?????????֐????Ƃɐ錾???Ȃ??Ă??A?X?N???v?g?̐擪?Ő錾????΂悳?????Ȃ??̂????A????ɂ͗??Ƃ?????????B

?@?܂?A?????̃X?N???v?g?t?@?C????A??????Ƃ??ɖ??ɂȂ?̂??B?S?̂?strict???[?h?ɂȂ??Ă???X?N???v?g?t?@?C???̌??ɁA?S?̂???strict???[?h?ɂȂ??Ă???X?N???v?g?t?@?C????A??????ƁA?A?????ʂ͑S?̂?strict???[?h?ɂȂ??Ă??܂????߁A??strict???[?h?̃X?N???v?g?̕????ŃG???[???o?Ă??܂??i?t?ɑS?̂???strict???[?h?̃X?N???v?g?t?@?C????strict???[?h?̃X?N???v?g?t?@?C????A??????ƁA?S?Ă???strict???[?h?ɂȂ??Ă??܂??ꍇ??????j?B???̂悤?Ȏ??Ԃ?????邽?߁Astrict???[?h?͊֐????Ƃɐ錾????????悢???낤?B

?@?Ȃ??A?֐??????q?ɂ??Ă???ꍇ?A?O???̊֐???strict???[?h??錾????Γ????̊֐??ł??L?????B

??Ή??u???E?U?ŋ??????ς???

?@?S?Ẵu???E?U??strict???[?h???T?|?[?g????Ă???킯?ł͂Ȃ??B?ŋ߂̃f?X?N?g?b?vPC?p?u???E?U?Ȃ?Ή????Ă??邪?A?Ⴆ??IE9?ȉ???Android 4.0?ȉ??ȂǁA??????ƌÂ??u???E?U?̒??ɂ͑Ή????Ă??Ȃ????̂?????B

?@??Ή??u???E?U?ł??Astrict???[?h?̐錾?͂????̕????񃊃e?????Ȃ̂ŁA?G???[?ɂȂ邱?Ƃ͂Ȃ??B???????A???????ς??ꍇ??????̂ŁAstrict???[?h??Ή??u???E?U?ł̃e?X?g?͌??????Ȃ??B

?@??Ƃ???eval?֐??ŋ??????ς???????̃R?[?h?Ɏ????B

// strict???[?h
(function () {
"use strict";
var z = 30;
// strict???[?h?ł́A???z?Ɖ???eval????z?͕ʕ?
var result = eval("var z = 45; z;");
// z=30, result=45
}());

// ??strict???[?h
(function () {
var z = 30;
// ??strict???[?h?ł́A???z?Ɖ???eval????z?͓?????
var result = eval("var z = 45; z;");
// z=45, result=45
}());

???[?h?ɂ???ċ??????ς???Ă??܂???iJavaScript?j
strict???[?h?ł́A???[?J???ϐ?z?ƁAeval?֐????Ő錾???Ă???ϐ?z?Ƃ͕ʕ??ɂȂ?̂ŁAeval?֐????s??????[?J???ϐ?z??30?̂܂܂??B?Ƃ??낪?A?????strict???[?h??Ή??̃u???E?U?Ŏ??s????ƁA?????̂悤??eval?֐????ł̑???????[?J???ϐ?z?ɑ΂??čs???Ă??܂????߁Aeval?֐????s??̃??[?J???ϐ?z??45?ɕς???Ă??܂??B
???̂悤?ȃ??[?h?ɂ???ċ??????ς???Ă??܂??R?[?h?́A?i?u???E?U??????ł??Ȃ??ꍇ?ɂ́j?????Ȃ??悤?ɂ??邵???Ȃ??B