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Sergey ufocoder

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@ufocoder
ufocoder / polyfill-isNan.js
Created October 21, 2018 11:56
Number.isNaN = Number.isNaN || (function(value) {
return value !== value;
})
@ufocoder
ufocoder / isNan.js
Created October 21, 2018 11:55
function isNan(value) {
return value !== value;
}
@ufocoder
ufocoder / nan_equality.js
Created October 21, 2018 11:55
var x = NaN;
console.log(x == NaN); // false
console.log(x === NaN); // false
@ufocoder
ufocoder / nan_check.js
Created October 21, 2018 11:54
console.log(isNaN(NaN)); // true
console.log(isNaN(null)); // false
console.log(isNaN(undefined)); // true
console.log(isNaN(Infinity)); // false
console.log(Number.isNaN(NaN)); // true
console.log(Number.isNaN(null)); // false
console.log(Number.isNaN(undefined)); // false
console.log(Number.isNaN(Infinity)); // false
@ufocoder
ufocoder / undeclared_typeof.js
Created October 21, 2018 11:53
console.log(undefined == null); // true
console.log(undefined === null); // false
@ufocoder
ufocoder / isNull.js
Created October 21, 2018 11:53
function isNull(value) {
return value === null;
}
@ufocoder
ufocoder / typeof_summary.md
Last active October 21, 2018 11:51
значение typeof
undefined "undefined"
null "object"
true or false "boolean"
all numbers or NaN "number"
all strings "string"
all symbols "symbol"
all functions "function"
all arrays "object"
@ufocoder
ufocoder / typechecks-with-typeof.js
Last active October 21, 2018 11:52
console.log(typeof ""); // "string"
console.log(typeof "hello"); // "string"
console.log(typeof String("hello")); // "string"
console.log(typeof new String("hello")); // "object"
console.log(typeof 0); // "number"
console.log(typeof -0); // "number"
console.log(typeof 0xff); // "number"
console.log(typeof -3.142); // "number"
console.log(typeof Infinity); // "number"
@ufocoder
ufocoder / tdz_typeof.js
Last active October 21, 2018 12:28
// Использование typeof для идентификатора,
// объявленного с блочной областью видимости,
// создаст ошибку `ReferenceError`
console.log(typeof tdzVariable === 'undefined'); // ReferenceError
const tdzVariable = 'I am initialized.';
@ufocoder
ufocoder / undeclared_typeof.js
Created October 20, 2018 19:46
console.log(undeclaredVariable === undefined); // ReferenceError
console.log(typeof undeclaredVariable === 'undefined'); // true