title: What do I have to use '+(x)+', '+(y)+' in D3? instead of using d3.event.x&d3.event.y?
body: <p>Always thank you guys for super kind and detailed guides.
  I just came across a curiosity in d3 syntax.
  I tried to move svg object imported from illustrator.
  Once I call drag function and move according to my mouse position, 
  it spits out related to x&amp;y position.</p>
  
  <p>This  question is not about meaning of += or ++.
  So please do not mark this question as a similar one as quesitons asknig meaning of +=.</p>
  
  <p><strong>However!</strong></p>
  
  <p>When I do the code below, </p>
  
  <pre><code>&lt;script&gt;
      var drag = d3.drag().on('drag',moving)
      // var xloc=5
      // var yloc=5
  
      function moving(){
    let xloc = d3.event.x
    let yloc = d3.event.y
    d3.selectAll('.furn1')
       .attr('transform','translate('+(xloc-250)+','+(yloc-250)+')')
    }
  
  
  
    d3.selectAll('g').classed('dragable',true)
    .call(drag)
  
  
  &lt;/script&gt;
  </code></pre>
  
  <p>The error is gone, and it works perfectly.</p>
  
  <p>What is </p>
  
  <p>'+( )+'</p>
  
  <p>in this code? and why just d3.event.x is not working?
  I checked d3.event.x by adding it with d3.event.y.
  And the console.log value was number which means d3.event.x is already number not string.</p>
  
  <p>Thank you guys in advance.</p>