Nodejs recursively validate filename for fswrite

user_10997312 0
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I am taking a long url string and parsing out the filename to save with fs.writefile(). Most of the stack answers say to use lastIndexOf('/'), but that does not work when there are multiple modifiers after the file name appears in the url. I have created a function that recursively removes the last section after the last '/' until a valid filename is found. What am I missing here? Why am I getting undefined?

exports.shortFileNameFn = (longUrlPath) => {
    if (longUrlPath) {
        //remove possible url querystring
        if (longUrlPath.lastIndexOf('?')>-1) longUrlPath=longUrlPath.substring(0,longUrlPath.lastIndexOf('?'));

        //recursively remove the section after the last '/' until a valid filename occurs
        const idx = longUrlPath.lastIndexOf('/');
        if (/^(?=[\S])[^\\ \/ : * ? " < > | ]+$/.test(longUrlPath.substring(idx + 1))) {         
            const validFileName = longUrlPath.substring(idx + 1);
            console.log(validFileName); //Returns SB_20Detail.jpg
            return validFileName;
        }
        //if name not yet valid, remove last section and call function again
        longUrlPath = longUrlPath.substring(0, idx);
        this.shortFileNameFn(longUrlPath);
    } 
};

//Calling code in app.js
const { shortFileNameFn } = require('./toStack');
const longProductImageUrl = 'https://img1.wsimg.com/isteam/ip/7ed83e96-6fb7-4d7c-bfe9-1a34fcbed15e/SB_20Detail.jpg/:/cr=t:31.25_25,l:0_25,w:100_25,h:37.5_25/rs=w:388,h:194,cg:true';
const shortProductImageUrl = shortFileNameFn(longProductImageUrl);
console.log('Short File Name:', shortProductImageUrl); //Returns undefined
node.js recursion validation url
1 Answers

You are calling shortFileNameFn recursively, but not returning the result. You can solve it with the following:

exports.shortFileNameFn = (longUrlPath) => {
    if (longUrlPath) {
        //remove possible url querystring
        if (longUrlPath.lastIndexOf('?')>-1) longUrlPath=longUrlPath.substring(0,longUrlPath.lastIndexOf('?'));

        //recursively remove the section after the last '/' until a valid filename occurs
        const idx = longUrlPath.lastIndexOf('/');
        if (/^(?=[\S])[^\\ \/ : * ? " < > | ]+$/.test(longUrlPath.substring(idx + 1))) {         
            const validFileName = longUrlPath.substring(idx + 1);
            console.log(validFileName); //Returns SB_20Detail.jpg
            return validFileName;
        }
        //if name not yet valid, remove last section and call function again
        longUrlPath = longUrlPath.substring(0, idx);
        return this.shortFileNameFn(longUrlPath);
    } 
};

To see the recursion happening, try adding a console.log in the beginning of the function shortFileNameFn and you should see it appear multiple times.

user_10865450
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