The most import thing is to let java project know the js builder.
#@#] sudo vi /home/A/myProj/proj_eclipse/src/.project
<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
<name>BBB</name>
<comment></comment>
<projects>
</projects>
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name> <!-- java builder => java project -->
<!-- <name>org.eclipse.wst.jsdt.core.javascriptValidator</name> --> <!-- js builder => js project -->
<arguments>
</arguments>
</buildCommand>
</buildSpec>
<natures>
<nature>org.eclipse.jdt.core.javanature</nature> <!-- java builder -->
<nature>org.eclipse.wst.jsdt.core.jsNature</nature> <!-- js -->
</natures>
</projectDescription>
Then <Your project>->right click-> Properties -> javascript -> Include Path -> Libraries -> add javascript libaray...
Have fun.