ui: use jsesc to pass args

packages/ui-default/backendlib/template.js

@@ -4,6 +4,7 @@ const yaml = require('js-yaml');
 const serialize = require('serialize-javascript');
 const nunjucks = require('nunjucks');
 const { filter } = require('lodash');
+const jsesc = require('jsesc');
 const argv = require('cac')().parse();
 const { findFileSync } = require('@hydrooj/utils/lib/utils');
 const status = require('@hydrooj/utils/lib/status');
@@ -66,6 +67,7 @@ class Nunjucks extends nunjucks.Environment {
     this.addFilter('ansi', (self) => misc.ansiToHtml(self));
     this.addFilter('base64_encode', (s) => Buffer.from(s).toString('base64'));
     this.addFilter('base64_decode', (s) => Buffer.from(s, 'base64').toString());
+    this.addFilter('jsesc', (self) => jsesc(self, { isScriptContext: true }));
     this.addFilter('bitand', (self, val) => self & val);
     this.addFilter('replaceBr', (self) => self.toString().replace(/\n/g, '<br>'));
     this.addFilter('toString', (self) => (typeof self === 'string' ? self : JSON.stringify(self, replacer)));