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- How to use isnan in js
- The isNaN() function checks whether a value is a non-numeric value (NaN). Usage: Pass the value to check as parameter, return true if it is NaN, otherwise return false. Note: isNaN() also returns true for strings, booleans, and null values. Use the Number.isFinite() function to check for a finite number. Use isNaN(value) !== true to check for undefined values.
- JS Tutorial 508 2024-05-01 09:45:24
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- What does sayname mean in js
- There is no built-in sayname function or keyword in JavaScript, its meaning depends on its usage in the specific code context: Custom function: Used to output or print the name in the given string. Object methods: used to get or set the name attribute stored in the object. Variable: Used to store a string that usually contains a person's name. Event handler: Used to output or print a predefined name when an event is triggered.
- JS Tutorial 642 2024-05-01 09:42:16
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- What are the basic data types in js
- There are six basic data types in JavaScript: boolean (true/false), null (empty value), undefined (undefined value), numeric value, string and symbol (unique identifier). The differences between these data types are their value range, representation, and purpose.
- JS Tutorial 395 2024-05-01 09:39:15
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- The meaning of this in js
- In JavaScript, the this keyword points to the object in the current execution context. Specifically: the global execution context points to the window object. The function execution context points to the object to which the function belongs. The method execution context points to the object of the calling method. The this object in the function inherits the parent function.
- JS Tutorial 296 2024-05-01 09:36:16
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- What do square brackets mean in js
- Square brackets are used for arrays in JavaScript. An array is an ordered data structure used to store a sequence of values. Square brackets have two main uses: one is to access array elements by element index, and the other is to modify array elements.
- JS Tutorial 515 2024-05-01 09:30:24
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- How to wrap alert in js
- In JavaScript, you can use the "\n" escape sequence to insert a newline character in a popup. This allows you to create multiple lines of text in a popup, making the information clearer and easier to read. "
- JS Tutorial 1074 2024-05-01 09:27:12
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- How to use alert in js
- The JavaScript alert() function is a pop-up window function. The user can specify a text string or a value to be converted to a string as a parameter, which is displayed in the prompt window and used to display a brief notification.
- JS Tutorial 898 2024-05-01 09:24:13
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- How to use question marks in js
- The question mark in JavaScript is a ternary operator, used to select one of two values based on a condition: Syntax: result = (condition) ? value 1 : value 2; condition: select value 1 if it is true, select value 2 if it is false .
- JS Tutorial 738 2024-05-01 09:18:13
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- What does !! in js mean?
- !! operator in JS: used to convert a value to a Boolean value. Operation: Perform logical NOT operation on the value. Then perform a logical NOT operation on the result. Result: true: when the value is not false, not the empty string, not null, not undefined. False: When the value is true, empty string, null, undefined. Purpose: Convert any value to a Boolean value. Forces an explicit conversion to a boolean value. Eliminate uncertain values.
- JS Tutorial 752 2024-05-01 09:15:27
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- What does % in js mean?
- Modulo operation is the remainder obtained after division operation. In JavaScript, % operator is used for modulo operation. This operator accepts dividend and divisor as operands. It is widely used in parity detection, random number generation, time unit conversion, and encryption technology.
- JS Tutorial 575 2024-05-01 09:12:16
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- What does !! in js mean?
- The !! operator in JavaScript converts any value to a boolean: true for non-zero, non-empty strings and objects, false for 0, null, undefined, NaN and empty strings. It is used to cast to boolean, invert boolean and implement lazy loading.
- JS Tutorial 996 2024-05-01 09:09:15
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- What does $ in js mean?
- The $ symbol in JavaScript represents a wildcard character that matches any character or the end of a specific string. Specific applications include: 1. Regular expression line end anchor; 2. Alias for selecting and operating elements in the jQuery library; 3. Alias for custom functions in some frameworks.
- JS Tutorial 700 2024-05-01 09:06:15
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- What does index mean in js
- Index in JavaScript represents the position of an element in an array or string, starting from 0. Use the index to access and modify elements through square bracket notation. Note that the index must be a non-negative integer and accessing a non-existent index will result in an error.
- JS Tutorial 510 2024-05-01 09:03:17
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- How to use filter function in js
- The JavaScript filter function is used to filter elements in an array that meet specific conditions and return a new array composed of elements that meet the conditions. Usage includes: filtering elements that meet simple or complex conditions, and creating filter chains. The filter function does not modify the original array. The callback function must return a Boolean value. If a Boolean value is not returned, an error will be thrown.
- JS Tutorial 713 2024-05-01 08:57:18
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- How to use typeof in js
- The typeof operator returns the type of the operand, and its syntax is: typeof operand. It returns one of the following string types: "undefined", "null", "boolean", "number", "bigint", "string", "symbol", or "object". Returning "object" null is a historical issue. Composite data structure
- JS Tutorial 858 2024-05-01 08:54:17
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