Exactly as @zulus said:
try to add activate="true" in javaCompletionProposalComputer and remove
what worked is:
<extension point="org.eclipse.wst.jsdt.ui.javaCompletionProposalComputer"
id="nodeclispe_textual_proposals"
name="Nodeclipse Text Proposals">
<proposalCategory icon="icons/npm/npm.gif"/>
</extension>
<extension point="org.eclipse.wst.jsdt.ui.javaCompletionProposalComputer"
id="NodeclipseProposals"
name="Nodeclipse Proposals">
<javaCompletionProposalComputer
class="org.nodeclipse.ui.contentassist.JSDTProposalComputer"
categoryId="org.eclipse.ui.texteditor.textual_proposals"
activate="true">
</javaCompletionProposalComputer>
</extension>
(source: nodeclipse.org)