Modify Table of Content Chapters Question

Question

Currently, my table of contents looks like this:

What command can I use to add the word "Chapter" before each chapter number? I want it to say:

"Chapter 1. Introduction..." instead of just "1 Introduction." and
"Chapter 2. Some Background Information..." instead of just "2 Some Background Information"

Currently, I'm using the following code to create the table of contents:

\usepackage {tocloft}

\renewcommand\cftchapdotsep{\cftdotsep}

\tableofcontents

Answer 1

You already use one macro from the tocloft package so why not use its additional facilities?

% chaptocprob.tex  SE 636777

\documentclass{book}

\usepackage{tocloft}
\renewcommand{\cftchapdotsep}{\cftdotsep}

\renewcommand{\cftchappresnum}{Chapter } % put this before the number
\addtolength{\cftchapnumwidth}{4em} % extra space for number and pre-name
\renewcommand{\cftchapaftersnum}{.} % put period after chapter number

\begin{document}

\tableofcontents

\chapter{Introduction}
\section{First section}

\end{document}

Answer 2

You wan't like this ?

\documentclass{book}
\usepackage{lipsum}
\usepackage{titletoc}
\titlecontents*{chapter}% <section-type>
[0pt]% <left>
{}% <above-code>
{\bfseries\chaptername\ \thecontentslabel\quad}% <numbered-entry-format>
{}% <numberless-entry-format>
{\bfseries\hfill\contentspage}% <filler-page-format>

\begin{document}
\tableofcontents
\chapter{Introduction} 
\section{First section}
\lipsum[1]
\chapter{Some Background Information}
\section{First section} \lipsum[2-3]
\section{Second section} \lipsum[4-5]
\section{Last section} \lipsum[6-7]
\end{document}