Created
March 11, 2023 05:29
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| Null Test: | |
| if (variable === null) | |
| - variable = ""; (false) typeof variable = string | |
| - variable = null; (true) typeof variable = object | |
| - variable = undefined; (false) typeof variable = undefined | |
| - variable = false; (false) typeof variable = boolean | |
| - variable = 0; (false) typeof variable = number | |
| - variable = NaN; (false) typeof variable = number | |
| Empty String Test: | |
| if (variable === '') | |
| -- or -- | |
| if (variable === "") | |
| - variable = ''; (true) typeof variable = string | |
| - variable = null; (false) typeof variable = object | |
| - variable = undefined; (false) typeof variable = undefined | |
| - variable = false; (false) typeof variable = boolean | |
| - variable = 0; (false) typeof variable = number | |
| - variable = NaN; (false) typeof variable = number | |
| Undefined Test: | |
| if (typeof variable == "undefined") | |
| -- or -- | |
| if (variable === undefined) | |
| - variable = ''; (false) typeof variable = string | |
| - variable = null; (false) typeof variable = object | |
| - variable = undefined; (true) typeof variable = undefined | |
| - variable = false; (false) typeof variable = boolean | |
| - variable = 0; (false) typeof variable = number | |
| - variable = NaN; (false) typeof variable = number | |
| False Test: | |
| if (variable === false) | |
| - variable = ''; (false) typeof variable = string | |
| - variable = null; (false) typeof variable = object | |
| - variable = undefined; (false) typeof variable = undefined | |
| - variable = false; (true) typeof variable = boolean | |
| - variable = 0; (false) typeof variable = number | |
| - variable = NaN; (false) typeof variable = number | |
| Zero Test: | |
| if (variable === 0) | |
| - variable = ''; (false) typeof variable = string | |
| - variable = null; (false) typeof variable = object | |
| - variable = undefined; (false) typeof variable = undefined | |
| - variable = false; (false) typeof variable = boolean | |
| - variable = 0; (true) typeof variable = number | |
| - variable = NaN; (false) typeof variable = number | |
| NaN Test: | |
| if (typeof variable == 'number' && !parseFloat(variable) && variable !== 0) | |
| -- or -- | |
| if (isNaN(variable)) | |
| - variable = ''; (false) typeof variable = string | |
| - variable = null; (false) typeof variable = object | |
| - variable = undefined; (false) typeof variable = undefined | |
| - variable = false; (false) typeof variable = boolean | |
| - variable = 0; (false) typeof variable = number | |
| - variable = NaN; (true) typeof variable = number |
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