How to check in node if module exists and if exists to load?

I need to check if file/(custom)module js exists under some path. I tried like

var m = require('/home/test_node_project/per');
but it throws error when there is no per.js in path. I thought to check with fs if file exists but I don't want to add '.js' as suffix if is possible to check without that. How to check in node if module exists and if exists to load ?

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最佳答案

Require is a synchronous operation so you can just wrap it in a try/catch.

try {
var m = require('/home/test_node_project/per');
// do stuff
} catch (ex) {
handleErr(ex);
}
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You can just check is a folder exists by using methods:

var fs = require('fs');


if (fs.existsSync(path)) {
// Do something
}


// Or


fs.exists(path, function(exists) {
if (exists) {
// Do something
}
});
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You can just try to load it and then catch the exception it generates if it fails to load:

try {
var foo = require("foo");
}
catch (e) {
if (e instanceof Error && e.code === "MODULE_NOT_FOUND")
console.log("Can't load foo!");
else
throw e;
}

You should examine the exception you get just in case it is not merely a loading problem but something else going on. Avoid false positives and all that.

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It is possible to check if the module is present, without actually loading it:

function moduleIsAvailable (path) {
try {
require.resolve(path);
return true;
} catch (e) {
return false;
}
}

Documentation:

require.resolve(request[, options])

Use the internal require() machinery to look up the location of a module, but rather than loading the module, just return the resolved filename.

Note: Runtime checks like this will work for Node apps, but they won't work for bundlers like browserify, WebPack, and React Native.


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