Problems encountered with the Replace() method in JS

This article mainly introduces a summary of the problems encountered when using the Replace() method in JS. Friends who need it can refer to it. I hope it can help everyone.

Today I encountered several problems when writing the automated packaging script for the PC client. Although it was a minor problem, it was stuck for a while, so I decided to record it.

The replace() method of js is used to replace certain content. It can receive two parameters. The first one is a regular expression object to be replaced or a string, and the second one can be the to-be-replaced regular expression object. The content or function to be replaced must be a string. The error I encountered during execution was: Cannot read property ‘replace’ of undefined. The specific code is as follows:

var fs=require("fs")
var infoPlistFile = osxFolder + '/Contents/Info.plist';
var infoPlist = fs.readFile(infoPlistFile);
fs.writeFile(infoPlistFile, infoPlist.replace(/Pexip Infinity Connect/gm, $scope.manifest.name));

When executing this code, the error reported was that the undefined attribute replacement cannot be obtained. At first, I didn’t know where the problem was. Then I tried to print out the replaced file infoPlist and found that It is null, and then I know that there is a problem in defining infoPlist. After changing it to fs.readFileSync, I found that there is no such error, but there is a new error: replace is not a function

Find Looking at the relevant information, it shows that the corresponding variable is not a string, but another type, so I printed the type of infoPlist, and what was printed was object, so the problem lies here, because the type of infoPlist is wrong, which resulted in an error. , so I added the operation of processing it into a string, so it worked

var infoPlistFile = osxFolder + '/Contents/Info.plist';
var infoPlist = readFile(infoPlistFile).toString();
writeFile(infoPlistFile, infoPlist.replace(/Pexip Infinity Connect/gm, $scope.manifest.name));

In addition, when I wrote the demo myself for testing, I also found that if there is no variable to receive, the replace() method cannot be used Function, such as:

var str="Hello World";
str.replace(/World/g, "dxy");
console.log(str);

The str printed out at this time is still "Hello World" and has not been replaced. A variable should be used as the receiver here to replace the original variable, such as:

var str="Hello World";
var a=str.replace(/World/g, "dxy");
console.log(a);

The printed result at this time is "Hello dxy".

Summary: This time when using the replace() method, I noticed the following problems:

1. When using the replace() method, you must first make sure that it cannot be in null or Called on a variable of undefined type. We can add a judgment to it, and only call the method if the variable has a value.

2. When executing the replace() method, the variable must not only have a value, but also must be of string type.

3. JS does not automatically assign values. To execute a method, you must either execute it directly in the method or return the result. When the result is returned, it needs to be received through a variable.

4. If the first parameter is a regular expression, quotation marks cannot be added.

Related recommendations:

Usage examples of replace() method in Javascript

Deprecated in ECSHOP: preg_replace() error Solution

Introduction to the use of php string replacement str_replace() function

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