Let’s talk about JavaScript operators

This article brings you relevant knowledge about javascript, which mainly introduces related issues about operators. Operators are also called operators and are used to implement assignment and comparison. and symbols that perform arithmetic operations and other functions. Let’s take a look at them together. I hope it will be helpful to everyone.

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Operator (operator) also Known as operators, they are symbols used to implement functions such as assignment, comparison, and performing arithmetic operations.

Commonly used operators in JavaScript are:

• Arithmetic operators
• Increment and decrement operators
• Comparison Operator
• Logical operator
• Assignment operator

Arithmetic operator

Concept: Symbols used in arithmetic operations, used to perform two operations Arithmetic operations on variables or values.

console.log(1 + 1); //2 console.log(1 - 1); //0 console.log(1 * 1); //1 console.log(1 / 1); //1 console.log(4 % 2); //0

Floating point numbers will have errors in arithmetic operations (avoid direct participation in operations):

console.log(0.1 + 0.2); //0.30000000000000004

Cannot directly determine whether two floating point numbers are equal.

var num = 0.1 + 0.2; console.log(num == 0.3); //false

• Arithmetic operator priority: multiplication and division first, addition and subtraction
• You can use the % remainder operator to determine whether a number is divisible

Expressions and return values:

Formulas composed of numbers, operators, variables, etc. are called expressions.

The expression will eventually return a result to us, which we call the return value.

Increment and decrement operators

If you need to repeatedly add or subtract 1 to a numeric variable, you can use increment ( ) and decrement (--) operator to complete.

Complicated writing:

var num = 1; num = num + 1; num = num + 1; console.log(num); //3

Preceding increment operator:

Write in the variable The front

num prefix increment is to add 1, similar to num=num 1

var age = 10; ++age; console.log(age);//11 类似于age = age + 1

Usage formula: Add self first, then return the value

console.log(age); var a = 10; console.log(++a + 10); //(10+1)+10=21

Postincrement operator

Write after the variable

num Setting increment means adding 1, similar to num=num 1

var age = 10; age++; console.log(age);//11 类似于age = age + 1

Usage formula: Return to the original value first, then increment

var a = 10; console.log(a++ + 10); //10+10=20 console.log(a); //11

Difference summary

• The pre-increment and post-increment operators can simplify the writing of code, making the variable value 1 easier to write than before.
• When used alone, the running results are the same.
• When used in conjunction with other codes, the execution results will be different.
• Preposition: add self first, then calculate ( put yourself first, then others)
• Postposition: first calculate the original value, then add yourself ( first, others Later, )
• When developing, post-increment/decrement is mostly used, and the code occupies one line. Example: num ;

Exercise:

var e = 10; var f = e++ + ++e; //1.e++=10 e=11 2.++e=12 f=10+12 console.log(f); //22

Comparison operator

Concept: Comparison operator (relational operator) is the operator used when comparing two data. After the comparison operation, a Boolean value (true/false) will be returned as the result of the comparison operation.

console.log(2 <= 5); //true console.log('岳泽以' = '个人博客'); //false console.log(17 == '17'); //true 默认转换数据类型，字符串型转换为数字型 console.log(17 = '17'); //false 数据类型不同，要求值和数据类型一致

console.log(3 > 5 && 3 > 2); //false console.log(3 < 5 && 3 < 7); //true

console.log(3 > 5 && 3 > 2); //false console.log(3 < 5 && 3 < 7); //true

console.log(!true); //false console.log(!false); //true

console.log(123 && 456); //返回456，除了0以外的所有数字都为真。 console.log(123 && 456 && 789); //返回789，依次后推 console.log(0 && 456); //0

console.log(123 || 456); //123 console.log(123 || 456 || 123 + 456); //123 console.log(0 || 456 || 123 + 456); //456

var num = 0; console.log(123 || num++); //逻辑中断造成num++未执行 console.log(num); //0

var num = 5; num += 10; console.log(num); //5+10=15 num *= 3; console.log(num); //15*3=45

console.log(4 >= 6 || '我' != '你' && !(12 * 2 == 144) && true); //true /* 逻辑运算符分四段 1.4 >= 6 得false 2.'我' != '你'得true 3.!(12 * 2 == 144)得ture 4.true 然后判断逻辑与：2与3得true 3和4得true 再判断逻辑或得：true */
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