title: Why am I getting Type 'Number' has no compatible call signatures. error?
body: <p>Hi I have this angular component code.</p>
  
  <pre><code>  private approvals: Approval[] = [];
  
    ngOnInit() {
      this.getUsersApprovals(this.userid);
    }
  
    getUsersApprovals(userid) {
      this.approvalsService.getUsersApprovals(userid).subscribe(
        data  =&gt; this.getSuccess(data),
        error =&gt; this.getError(error)
      );
    }
  
   private getSuccess(data) {
      this.approvals = data;
      let approval_count = this.approvals.length;
    }
  </code></pre>
  
  <p>And when I execute <code>this.approvals.length</code> I get this error:</p>
  
  <pre><code>Cannot invoke an expression whose type lacks a call signature. Type 'Number' has no compatible call signatures.
  </code></pre>
  
  <p>What am I doing wrong here?</p>
  
  <p>Update:</p>
  
  <p>I was able to archive the affect I wanted by doing this instead ...</p>
  
  <pre><code>let approval_count = data.length;
  </code></pre>
  
  <p>... but I still don't understand what was wrong with:</p>
  
  <pre><code>    let approval_count = this.approvals.length;
  </code></pre>