Detailed explanation of JavaScript numerical methods and properties
This article brings you relevant knowledge about javascript, which mainly introduces issues related to numerical methods and properties in JavaScript, including toSting, toFixed, toPrecision, etc., as follows Let's take a look, I hope it will be helpful to everyone.
[Related recommendations: javascript video tutorial, web front-end]
We know that in JavaScript, Not only do reference types have methods and properties, but the three basic data types of string, number, and boolean also have methods and properties.
Today we are going to compare the properties and properties of literal values (strictly speaking, they should be Number objects). A summary of common methods is helpful for our systematic learning and mastering
Number object methods
All number methods can be used for any type of number (literal, variable or expression)
1. toSting() method
- Returns a numerical value as a string
Example:
var num = 100 var str = num.toString() // 变量 var str1 = (99).toString() // 字面量 var str2 = (100+99).toString() // 表达式 console.log(str) // '100' console.log(str1) // '99' console.log(str2) // '199'
2 . toFixed() method
- Returns a string value, which contains a number with the specified number of decimal places (will be rounded)
Parameters: Receives a number indicating precision
Example:
var num = 9.656 var num1 = num.toFixed(0) var num2 = num.toFixed(2) var num3 = num.toFixed(4) console.log(num1) // 10 console.log(num2) // 9.66 console.log(num3) // 9.6560
3. toPrecision() method
- Returns a string value, which contains A number with a specified length
Parameter: Receive a number, indicating the total number of digits
Example:
var num = 9.656 var num1 = num.toPrecision() // 省略参数表示原数 var num2 = num.toPrecision(2) var num3 = num.toPrecision(4) console.log(num1) // 9.656 console.log(num2) // 9.7 console.log(num3) // 9.656
4. toExponential( ) Method
- Returns a string value that contains a number that has been rounded and used exponential notation
Parameters: Receives a number, defining the number of characters after the decimal point
Example:
var num = 9.656 var num1 = num.toExponential(2) // 省略参数表示原数 var num2 = num.toExponential(4) ar num3 = num.toExponential(6) console.log(num1) // 9.66e+0 console.log(num2) // 9.6560e+0 console.log(num3) // 9.656000e+0
5. valueOf() method
- Return the value as a numerical value
Example:
var num = 100 var num1 = num.valueOf() // 变量 var num2 = (99).valueOf() // 字面量 var num3 = (100+99).valueOf() // 表达式 console.log(num1) // 100 console.log(num2) // 99 console.log(num3) // 199
Note: Basically, this method will not be used for values in the code, because the valueOf() method is used internally in JavaScript to convert the Number object into a primitive value
TIPS: All JavaScript data types have valueOf() and toString() methods
Convert variables into numbers
These three JS methods can be used to convert variables into numbers
Number() method
parseInt() method
parseFloat() Methods
It should be noted that these methods are global methods, not methods of numerical objects
Number object properties (not commonly used)
MAX_VALUE Returns the maximum number possible in JS
MIN_VALUE Returns the minimum number possible in JS
NEGATIVE_INFINITY Indicates negative Infinity
- ## NaN ‖ ional in infinity_NaN ure - MAX_VALUE Returns the largest possible number in JavaScript
- MIN_VALUE Returns the smallest possible number in JavaScript Example:
var x = Number.MAX_VALUE var y = Number.MIN_VALUE console.log(x) // 1.7976931348623157e+308 console.log(y) // 5e-324POSITIVE_INFINITY Represents positive infinity (overflow Return on time) NEGATIVE_INFINITY Represents negative infinity (return on overflow) Example:
var x = 1 / 0 var y = -1 / 0 console.log(x) // Infinity console.log(y) // -InfinityNaN Non-number NaN is a reserved word in JavaScript and represents NaN is an illegal number (not a number) Example:
var x = 100 / 'apple' console.log(x) // NaNNumeric attributes cannot be used for variables Numeric attributes belong to the JavaScript number object wrapper named number In layman’s terms, these properties can only be accessed by Number.MAX_VALUE Example:
var x = 6 var y = x.MAX_VALUE // 变量访问 var z = Number.MAX_VALUE // 数字对象访问 console.log(y) // undefined console.log(z) // 1.7976931348623157e+308[Related recommendations:
javascript video tutorial
,web front end
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