JavaScript ã®ä¾å¤ "property is non-configurable and can't be deleted" ã¯ãããããã£ãåé¤ãããã¨ãããããã®ããããã£ãæ§æä¸å¯ã§ããå ´åã«çºçãã¾ãã
ã¨ã©ã¼ã¡ãã»ã¼ã¸TypeError: Calling delete on 'x' is not allowed in strict mode (Edge)
TypeError: property "x" is non-configurable and can't be deleted. (Firefox)
TypeError: Cannot delete property 'x' of #<Object> (Chrome)
ã¨ã©ã¼ã®ç¨®é¡
strict ã¢ã¼ãã§ã®ã¿ãTypeError
ã®è¦åãåºã¾ãã
ããããã£ãåé¤ãããã¨ãã¾ããããããããã£ã non-configurable ã§ãããconfigurable
屿§ã¯ããªãã¸ã§ã¯ãããããããã£ãåé¤ã§ãããã©ãããããã³ (writable
ãé¤ã) 屿§ã夿´ã§ãããã©ãããå¶å¾¡ãã¾ãã
ãã®ã¨ã©ã¼ã¯ãstrict ã¢ã¼ãã®ã³ã¼ã ã§ã®ã¿çºçãã¾ããé strict ã³ã¼ãã§ã¯ããã®æä½ã¯ false
ãè¿ãã¾ãã
æ§æä¸å¯ã®ããããã£ã¯ããã»ã©ä¸è¬çã§ã¯ããã¾ããããObject.defineProperty()
ã Object.freeze()
ã使ç¨ãã¦çæãããã¨ãã§ãã¾ãã
"use strict";
var obj = Object.freeze({ name: "Elsa", score: 157 });
delete obj.score; // TypeError
("use strict");
var obj = {};
Object.defineProperty(obj, "foo", { value: 2, configurable: false });
delete obj.foo; // TypeError
("use strict");
var frozenArray = Object.freeze([0, 1, 2]);
frozenArray.pop(); // TypeError
JavaScript ã«çµã¿è¾¼ã¾ãããå°æ°ã®æ§æä¸å¯ããããã£ãããã¾ãããããããããMath ã®å®æ°ãåé¤ãããã¨ããã®ããããã¾ããã
"use strict";
delete Math.PI; // TypeError
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