Summary of string concatenation technology in JavaScript

JavaScript is a programming language used to create interactive web pages. It is an important foundation for Web front-end development. In JavaScript, concatenating strings is a very common and important operation. In many cases, we need to concatenate one or more strings to form a new string to meet specific needs. This article will introduce string concatenation technology in JavaScript and several common implementation methods.

1. Use the plus operator to splice strings

The most common way to splice strings in JavaScript is to use the plus operator ( ). The plus sign can concatenate strings and other values, such as numbers or variables, in expressions. For example:

var str1 = "Hello";
var str2 = "World";
var res = str1 + " " + str2;
console.log(res); //输出 "Hello World"

In the above code, two string variables str1 and str2 are first declared, and their values ​​are set to "Hello" and "World" respectively. Then use the plus sign to concatenate the two strings with a space in between, and finally assign the result to the variable res. The result is output through console.log(), and the result is "Hello World".

It should be noted that when using the plus operator to splice strings, you should follow two principles:

1. Add necessary spacers between strings to facilitate reading.

2. Convert the string to ensure the correct data type.

For example:

var str1 = "10";
var str2 = "20";
var res = str1 + str2;
console.log(res); //输出 "1020"

The above code means that by splicing the string variables str1 and str2, the generated result is "1020", not 30. This is because the plus operator, when used to concatenate strings, only concatenates the strings together and does not perform the operation of adding numbers. If you want to add numbers, you need to convert the strings into numbers, for example:

var num1 = parseInt(str1);
var num2 = parseInt(str2);
var res = num1 + num2;
console.log(res); //输出 30

2. Use the concat() method to splice strings

In addition to the plus operator, JavaScript also provides A concat() method can be used to concatenate two or more strings. For example:

var str1 = "Hello";
var str2 = "World";
var res = str1.concat(" ", str2);
console.log(res); //输出 "Hello World"

In this example, two string variables str1 and str2 are declared and connected using the concat() method with a space in between. Finally, save the results to the variable res and use console.log() to output the results.

It should be noted that when using the concat() method, the string to be connected must be passed to the concat() method as a parameter. For example:

var str1 = "Hello";
var str2 = "World";
var res = str1.concat(str2);
console.log(res); //输出 "HelloWorld"

In this example, the concat() method only accepts one parameter, str2, so the first string "Hello" and str2 will automatically be concatenated into one string "HelloWorld". If you need to add a space or other characters between two strings, you need to use a comma between the string variables and write the space or other characters after the comma.

3. Use template strings to splice strings

In ES6 (ECMAScript 6), JavaScript has added a new string splicing method - template strings. It can be defined via backticks (`), using ${} to enclose JavaScript expressions. For example:

var str1 = "Hello";
var str2 = "World";
var res = `${str1} ${str2}`;
console.log(res); //输出 "Hello World"

In this example, backticks are used to define the string variables str1 and str2 in the template string, and ${} is used to include them, adding a between the two strings. Space. Finally, assign the result to the variable res and use console.log() to output the result.

It should be noted that when using template strings to splice strings, you should pay attention to the following points:

1. In the template string, any characters and expressions can be included, and No need to use delimiters.

2. When using ${} to include an expression, you cannot include statements, only a single expression.

3. Using template strings makes it easier to splice multiple complex strings, avoiding the need to use the plus sign or concat() method for multiple splicings.

Summary

The above are the three commonly used string splicing methods in JavaScript: using the plus operator, using the concat() method and using template strings. In actual development, you should choose the appropriate way to splice strings according to the specific situation to ensure the running efficiency of the program and the readability of the code.

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