How to implement addition, subtraction, multiplication and division operations in javascript

Implementation method: 1. Use the " ", "-", "*", "/" and "%" characters to realize addition, subtraction, multiplication, division and remainder operations; 2. Use " =", "-=", "*=", and "/=" symbols will first perform addition, subtraction, multiplication, and division operations, and then assign the results to the variables on the left side of the operator; 3. Use the "x" or "x" symbol The value of the variable is incremented (1), and the "--x" or "x--" character is used to decrement the value of the variable (-1).

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

In javascript, you can use operators to implement the four arithmetic operations of addition, subtraction, multiplication and division. Operators are symbols used to tell the JavaScript engine to perform a certain operation. For example, the plus sign ( ) represents addition, and the minus sign (-) represents subtraction.

1: Arithmetic operators

Arithmetic operators are used to perform common mathematical operations, such as addition, subtraction, multiplication, division, etc. The following table lists the arithmetic operators supported in JavaScript:

Operator	Description	Example
	Addition operator	x y means calculating the sum of x plus y
-	Subtraction operation Symbol	x - y means calculating the difference between x minus y
*	Multiplication operator	x * y means calculating Product of x times y
/	Division operator	x / y means calculating the quotient of x divided by y
%	Modulo (remainder) operator	x % y means calculating the remainder of x divided by y

Addition operator

Example 1

Pay attention to the summation operation of special operands.

var n = 5;  //定义并初始化任意一个数值
console.log(NaN + n);  //NaN与任意操作数相加，结果都是NaN
console.log(Infinity + n);  //Infinity与任意操作数相加，结果都是Infinity
console.log(Infinity + Infinity);  //Infinity与Infinity相加，结果是Infinity
console.log((-Infinity) + (-Infinity));  //负Infinity相加，结果是负Infinity
console.log((-Infinity) + Infinity);  //正负Infinity相加，结果是NaN

Example 2

The addition operator can decide whether to add or connect based on the data type of the operands.

console.log(1 + 1);  //如果操作数都是数值，则进行相加运算
console.log(1 + "1");  //如果操作数中有一个是字符串，则进行相连运算
console.log(3.0 + 4.3 + "");  //先求和，再连接，返回"7.3"
console.log(3.0 + "" + 4.3);  //先连接，再连接，返回"34.3"
                              //3.0转换为字符串3

When using the addition operator, you should first check whether the data type of the operand meets the requirements.

Subtraction operator

Example 1

Pay attention to the subtraction operation of special operands.

var n = 5;  //定义并初始化任意一个数值
console.log(NaN - n);  //NaN与任意操作数相减，结果都是NaN
console.log(Infinity - n);  //Infinity与任意操作数相减，结果都是Infinity
console.log(Infinity - Infinity);  //Infinity与Infinity相减，结果是NaN
console.log((-Infinity) - (-Infinity));  //负Infinity相减，结果是NaN
console.log((-Infinity) - Infinity);  //正负Infinity相减，结果是-Infinity

Example 2

In the subtraction operation, if the operand is a string, try to convert it into a numerical value before performing the operation. If one of the operands is not a number, NaN is returned.

console.log(2 - "1");  //返回1
console.log(2 - "a");  //返回NaN

Use value minus 0 to quickly convert a value to a number. For example, query strings in HTTP requests are generally string numbers. You can first subtract 0 from these parameter values ​​to convert them into numerical values. This has the same result as calling the parseFloat() method, but the subtraction is more efficient and faster. Implicit conversions with the subtraction operator return NaN if they fail, which is different from the return value when performing the conversion using the parseFloat() method.

For example, for the string "100aaa", the parseFloat() method can parse out the first few numbers, but for the subtraction operator, it must be a complete number before it can be converted.

console.log(parseFloat("100aaa"));  //返回100
console.log("100aaa" - 0);  //返回NaN

For Boolean values, the parseFloat() method can convert true to 1 and false to 0, while the subtraction operator treats it as NaN.

For objects, the parseFloat() method will try to call the object's toString() method for conversion, while the subtraction operator first tries to call the object's valueOf() method for conversion, and then calls toString() after failure. Make the conversion.

Multiplication operator

Pay attention to the multiplication operation of special operands.

var n = 5;  //定义并初始化任意一个数值
console.log(NaN * n);  //NaN与任意操作数相乘，结果都是NaN
console.log(Infinity * n);  //Infinity与任意非零正数相乘，结果都是Infinity
console.log(Infinity * (- n));  //Infinity与任意非零负数相乘，结果是-Infinity
console.log(Infinity * 0);  //Infinity与0相乘，结果是NaN
console.log(Infinity * Infinity);  //Infinity与Infinity相乘，结果是Infinity

Division operator

Pay attention to the division operation of special operands.

var  n = 5;  //定义并初始化任意一个数值
console.log(NaN / n);  //如果一个操作数是NaN，结果都是NaN
console.log(Infinity / n);  //Infinity被任意数字除，结果是Infinity或-Infinity
                            //符号由第二个操作数的符号决定
console.log(Infinity / Infinity);  //返回NaN
console.log(n / 0);  //0除一个非无穷大的数字，结果是Infinity或-Infinity，符号由第二个操作数的符号决定
console.log(n / -0);  //返回-Infinity，解释同上

Remainder operator

Remainder operation is also called modular operation. For example:

console.log(3 % 2);  //返回余数1

Modular operation mainly operates on integers and is also applicable to Floating point number. For example:

console.log(3.1 % 2.3);  //返回余数0.8000000000000003

Example

Pay attention to the remainder operation of special operands.

var n = 5;  //定义并初始化任意一个数值
console.log(Infinity % n);  //返回NaN
console.log(Infinity % Infinity);  //返回NaN
console.log(n % Infinity);  //返回5
console.log(0 % n);  //返回0
console.log(0 % Infinity);  //返回0
console.log(n % 0);  //返回NaN
console.log(Infinity % 0);  //返回NaN

2: Assignment operator

The assignment operator is used to assign values ​​to variables. It has the following two forms:

• Simple assignment operation =: Copy the value of the operand on the right side of the equal sign directly to the operand on the left side, so the value of the operand on the left side will change.

• Assignment operation of additional operations: Before assignment, perform some operation on the right operand, and then copy the operation result to the left operand.

The assignment operations of some additional operations can realize the four arithmetic operations of addition, subtraction, multiplication and division. The specific description is as shown in the table:

Assignment operator that implements the additional operations of the four arithmetic operations of addition, subtraction, multiplication and division

Assignment operator	Explanation	Example	Equivalent to
=	Addition or concatenation operation and assignment	a = b	a = a b
-=	Subtraction operation and assignment	a -= b	a= a - b
*=	Multiplication and assignment	a *= b	a = a * b
/=	Division operation and assignment	a /= b	a = a / b
%=	Modulo operation and assignment	a %= b	a = a % b

The sample code is as follows:

var x = 10;
x += 20;
console.log(x);  // 输出：30
var x = 12,
    y = 7;
x -= y;
console.log(x);  // 输出：5
x = 5;
x *= 25;
console.log(x);  // 输出：125
x = 50;
x /= 10;
console.log(x);  // 输出：5
x = 100;
x %= 15;
console.log(x);  // 输出：10

3: Self-increment and self-decrement operators

Self-increment and self-decrement operators Used to increment (1) and decrement (-1) the value of a variable. The following table lists the increment and decrement operators supported in JavaScript:

## xIncrement operatorIncrements x 1, then return the value of xx Increment operatorReturn the value of x, and then add 1 to x--xDecrement operatorDecrease x by 1 and return the value of x##x --The sample code is as follows:

Operator	Name	Affect
Decrement operator	Returns the value of x, and then decrements x by 1

var x;

x = 10;
console.log(++x);  // 输出：11
console.log(x);    // 输出：11

x = 10;
console.log(x++);  // 输出：10
console.log(x);    // 输出：11

x = 10;
console.log(--x);  // 输出：9
console.log(x);    // 输出：9

x = 10;
console.log(x--);  // 输出：10
console.log(x);    // 输出：9

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