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How to implement explicit conversion and implicit conversion in javascript

亚连
亚连Original
2018-06-20 16:21:511542browse

The editor below will share with you an article about explicit conversion and implicit conversion (detailed explanation) based on javascript. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor and take a look.

Display conversion

1. Question: Please enter your age this year and ask for 5 years How old will you be?

//a.prompt接收到的数据是string类型的。
var age = prompt("请输入你今年的年龄");
alert(typeof age);
var age5 = age + 5; // 这里只会拼接成了15,而不是加5
alert("我今年"+age+"岁了,5年后我"+age5+"岁了");

2. The string must be converted into number type.

In response to the above problem, age needs to be converted into a numeric type

2.1 You can use Number (the content that needs to be converted);

var str = true;
  var num = Number(str);
  console.log(num); //1 
  console.log(typeof num); //number
  // 注意:
  // 1.如果这个转换的字符串本身就是一个数字,那么可以转换成功; 如果这个字符串本身不是一个数字,那么转成NaN.
  // 2.如果这个字符串本身是一个数字,前后有空格,也是会转换成功的; 如果中间有空格,就转成NaN.
  // 3.如果是一个"",或者是" ",或者是flase,那么会转换成0.true转成1,undefined转成NaN
  // 4.如果字符串的本身是一个小数,也是可以转换成功的。

2.2 You can use parseInt (required Content to be converted);

var str = "123";
var num = parseInt(str);
console.log(num); //123
console.log(typeof num); //number
//  注意:
//  1.从左往右查找,直到遇到第一个非数字为止,前面的所有的内容转换成数字。
//  2.如果找完了,都没有找到一个数字,那么就转换成NaN.
//  3."" 和 "  " 转化成NaN
//  4.如果字符串里面是小数,那么转换后只能得到他的整数部分。

2.3 You can use parseFloat(Content to be converted);

var str = "123.24ll";
var num = parseFloat(str);
console.log(num); //123.24
console.log(typeof num); //number
// 注意:如果字符串里面是小数,那么转换后还是小数。。
//******注意: true会转成1,false会转换0.
// 如果字符串转数字,一般的使用parseInt或者parseFolat。
// 如果是其他类型,比如布尔类型,使用Number();

3. Other types of data are converted into string types.

3.1 You can use String (the content that needs to be converted);

var num = 123;
var str = String(num);
console.log(str); //"123"
console.log(typeof str); //string
//注意: "123"  "true" "false" "undefined"  "null" "NaN"

3.2 You can use the content that needs to be converted.toString();

var num = 123;
var str = num.toString();
console.log(str); //"123"
console.log(typeof str); //string
//注意: "123"  "true" "false "NaN"
//undefined 和null 不能使用toString。

4 .Other data types are converted into boolean types.

4.1 You can use Boolean (the content that needs to be converted);

var num = "";
var res = Boolean(num);
console.log(res); //false
console.log(typeof res); //boolean
//注意:
//那些可以转换成布尔类型的false: 0 -0  false "" undefined null NaN
//" "会转换成true

Implicit conversion

1. Convert other types to number type.

1.1 You can add a positive sign in front of the content that needs to be converted.

var str = "123";
var res = +str;
console.log(res); //123
console.log(typeof res); //number

1.2 The content that needs to be converted can be used for arithmetic operations and cannot be used later.

var str = "123";
var res = str * 1;
console.log(res); //123
console.log(typeof res); //number
//注意: 一定要和连接符做一个区分。

2. Other types can be converted into string type. Use the connector ""

var num = 123;
var str = num + "";
console.log(str); //"123"
console.log(typeof str);//string

3. Convert other types to boolean type. Use the negation operator

var num = undefined;
var res = !!num;
console.log(res); //false
console.log(typeof res);boolean
// 注意:那些能转成布尔类型的false:0 -0 false undefiend null NaN ""

1. Question: Please enter your age this year and find out how old you will be in 5 years.

//a.prompt接收到的数据是string类型的。
var age = +prompt("请输入你今年的年龄");
var age5 = age + 5;
alert("我今年"+age+"岁了,5年后我"+age5+"岁了");

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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