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- The difference between var and const in js
- In JavaScript, the main difference between var and const is that variables declared with var can be reassigned and redeclared, while constants declared with const cannot be modified. Variables declared with var are available within the function or global scope, whereas variables declared with const are only available within the block or module in which they are declared. A var variable can be declared repeatedly in the same scope, while a const variable cannot be declared repeatedly. A var declaration can be anywhere in the block, while a const declaration must be at the top of the block or module.
- JS Tutorial 286 2024-05-01 07:51:17
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- How to use escape characters in js
- JavaScript escape characters are used to represent special characters in strings, using a backslash (\) followed by a specific sequence of characters. Common escape characters include: newline (\n), tab (\t), backslash (\), single quotation mark (\'), double quotation mark (\"), null character (\0), and replace Page break (\f) and carriage return (\r). Can be used to represent unprintable characters, escape special characters, and insert special symbols.
- JS Tutorial 376 2024-05-01 07:48:17
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- There are several ways of for loop in js
- There are three types of for loops in JavaScript: the basic for loop is used to iterate over quantitative values; the for...in loop is used to iterate over object keys; and the for...of loop is used to iterate over the elements of an iterable object.
- JS Tutorial 798 2024-05-01 07:42:13
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- How to write arrow function in js
- Arrow function is a shorthand function syntax, written as: (parameters) => expression. Its features include conciseness, the use of lexical scope binding, and no own this binding. Compared with traditional functions, arrow functions are more concise, lexically scoped, and have no this binding. Arrow functions are commonly used for callback functions, compact functions, and lexically scoped functions.
- JS Tutorial 686 2024-05-01 07:33:16
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- How to write if to judge multiple conditions in js
- Ways to evaluate multiple conditions in JavaScript include using the || (or) operator, the && (and) operator, nested if statements, and switch statements (which only work when comparing one value).
- JS Tutorial 704 2024-05-01 07:30:24
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- How to use if else in js
- JavaScript's if else statement is used to execute a code block based on a condition. The syntax is: if (condition) { code block } else { code block }. It can be nested to create complex branching logic. Conditions can evaluate to boolean values, else statements are optional, and additional branch conditions can be added using else if statements.
- JS Tutorial 275 2024-05-01 07:27:16
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- How to use if function in js
- JavaScript’s if function is used to execute a block of code based on a condition. When the condition is true, the code block is executed; when the condition is false, the code block is skipped. It supports nested, else clauses and else if clauses for handling complex conditions.
- JS Tutorial 765 2024-05-01 07:24:14
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- The difference between const and var in js
- In JavaScript, const and var are keywords used to declare variables. They have the following differences in scope, mutability and initial value: Scope: const is only valid within the block-level scope where it is declared, while var is valid throughout the Valid within function scope. Mutability: Once declared, a const variable cannot be changed, whereas a var variable can be reassigned. Initial value: const variables must be initialized when declared, while var variables do not need to be initialized, and the default value is undefined.
- JS Tutorial 417 2024-05-01 07:18:17
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- The difference between let and var defining variables in js
- Let and var are used to define variables in JavaScript. The difference is: scope: var variables are valid within the entire function or global scope, while let variables are only valid within the block where they are declared. Scope hoisting: var variables are hoisted to the top of the function or global scope before script execution, while let variables are not hoisted. Redeclaration: var allows variables to be redeclared within the same scope, while let does not. Best practices recommend using let instead of var for tighter scoping and hoisting behavior.
- JS Tutorial 768 2024-05-01 07:15:26
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- or how to express it in js
- In JavaScript, the || operator is used for logical "OR" operations. If the first Boolean operand is true, the first operand is returned, otherwise the second operand is returned, with lower priority than the && operator. Higher than the assignment operator.
- JS Tutorial 672 2024-05-01 07:09:14
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- How to get the current date in js
- To get the current date in JavaScript, you can use the following methods: Date.now() Returns the number of milliseconds that have elapsed since January 1, 1970. new Date() returns a Date object representing the current moment. The following methods can be used to obtain the date component: getFullYear(), getMonth(), getDate(), getHours(), getMinutes(), getSeconds(). You can use the following methods to format dates: toLocaleDateString(), toLocaleTimeString(), toISOSt
- JS Tutorial 523 2024-05-01 07:06:15
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- What does isnan mean in js
- isNaN is a function in JavaScript that checks whether a value is not a number. It takes one argument and returns a Boolean value: true if it is NaN, false otherwise. isNaN can be used to validate input and ensure that the number format is correct. It is suitable for numeric literals, variables and expressions. It should be noted that NaN is different from other numeric values (including 0). Even if the input is an empty string, isNaN returns true.
- JS Tutorial 1065 2024-05-01 06:54:14
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- The reason why NaN appears in js
- NaN (not a number) can appear in JavaScript due to invalid string conversions, invalid operations in mathematical operations, accessing uninitialized variables, the return value of the isNaN() function, and other specific situations.
- JS Tutorial 255 2024-05-01 06:48:15
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- How to find elements in js
- Methods to find elements in JavaScript are: getElementById(id): Use element ID to find elements. getElementsByClassName(className): Find elements using class names. getElementsByTagName(tagName): Find elements using tag names. querySelectorAll(selector): Find elements using CSS selectors. querySelector(selector): Use a CSS selector to find the first matching element.
- JS Tutorial 480 2024-05-01 06:45:22
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- How to display seconds in countdown timer in js
- In JavaScript, you can implement a countdown timer and display the remaining seconds by using the setInterval() function: determine the number of seconds to count down; create the remaining seconds variable; use the setInterval() function to check the remaining seconds every second and update the display; when the remaining seconds When the number reaches 0, the timer is cleared.
- JS Tutorial 1040 2024-05-01 06:42:16
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