Yesterday, I saw a question in MSDN forums on how to programmatically read SharePoint List items using JavaScript. Here is the full workable code below :-

var siteUrl = '/sites/MySiteCollection';

function retrieveListItems() {

    var clientContext = new SP.ClientContext(siteUrl);
    var oList = clientContext.get_web().get_lists().getByTitle('YourCustomList');
        
    var camlQuery = new SP.CamlQuery();
    camlQuery.set_viewXml('<View><Query><Where><Geq><FieldRef Name='ID'/>' + 
        '<Value Type='Number'>1</Value></Geq></Where></Query><RowLimit>10</RowLimit></View>');
    this.collListItem = oList.getItems(camlQuery);
        
    clientContext.load(collListItem);
        
    clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceeded), Function.createDelegate(this, this.onQueryFailed));        
        
}

function onQuerySucceeded(sender, args) {

    var listItemInfo = '';

    var listItemEnumerator = collListItem.getEnumerator();
        
    while (listItemEnumerator.moveNext()) {
        var oListItem = listItemEnumerator.get_current();
        listItemInfo += 'nID: ' + oListItem.get_id() + 
            'nTitle: ' + oListItem.get_item('Title') + 
            'nBody: ' + oListItem.get_item('Body');
    }

    alert(listItemInfo.toString());
}

function onQueryFailed(sender, args) {

    alert('Request failed. ' + args.get_message() + 'n' + args.get_stackTrace());
}

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