How do I re-write this Javascript code to avoid JSHint warning?

Question

I'm a newbie developing a small web application that uses HTML, JavaScript (Angular 1.5.0) & CSS. I am using Grunt to process, jslint, minify my javascript and CSS files. My Javascript code includes an SVG image created by d3.js.

I'm currently getting the following warning from jshint:

line 1932  col 32  Don't make functions within a loop.

How can I rewrite the code below to eliminate this warning?

Line #1924        for (var j = 0; j <= 5; j++) {
Line #1925          var myVarX = j * 100;
Line #1926          var myVarY = j * 200;
Line #1927          var myText = self.svgContainer.append("text")
Line #1928            .attr("x", myVarX)
Line #1929            .attr("y", myVarY)
Line #1930            .text("Hello World")
Line #1931            .attr("fill", "black")
Line #1932            .attr("transform", function(d){
Line #1933                var bb = this.getBBox();
Line #1934                leftBoundary = bb.x + (bb.width / (-2));
Line #1935                return "translate(" + (bb.width / (-2)) + ", 0)";
Line #1936              }
Line #1937            )
Line #1938          if (leftBoundary > centerX + 5)
Line #1939            myText.style("display", "block");
Line #1940          else
Line #1941            myText.remove();
Line #1942        }

Answer 1

Move this

function(d){
    var bb = this.getBBox();
    leftBoundary = bb.x + (bb.width / (-2));
    return "translate(" + (bb.width / (-2)) + ", 0)";
}

outside the scope of the for loop. Like:

var transformCallback = function(d) { 
    var bb = this.getBBox();
    ...

and then use transformCallback in place of the function.

.attr("transform", transformCallback)

Answer 2

Function.prototype.getTransform = function() {
  var bb = this.getBBox();
  leftBoundary = bb.x + (bb.width / (-2));
  return "translate(" + (bb.width / (-2)) + ", 0)";
};

...

for (var j = 0; j <= 5; j++) {
  var myVarX = j * 100;
  var myVarY = j * 200;
  var myText = self.svgContainer.append("text")
    .attr("x", myVarX)
    .attr("y", myVarY)
    .text("Hello World")
    .attr("fill", "black")
    .attr("transform", this.getTransform())
  if (leftBoundary > centerX + 5)
    myText.style("display", "block");
  else
    myText.remove();
}

Answer 3

Line 1924 : Change `j++` to `j+=1`
Line 1932: Take out the function def outside the loop. Define it outside and use it here 

// function defined outside the loop
function transformFn(d) {
  var bb = this.getBBox(); // if using jQuery replace this with $(this) or that/self to ensure correct this binding
  leftBoundary = bb.x + (bb.width / (-2));
  return "translate(" + (bb.width / (-2)) + ", 0)";
}


// function used at Line1932 
.attr('transform', transformFn)

Rest looks good to me.

Answer 4

Another more D3-ish approach will get rid of the outer for-loop altogether. Whenever you come across a for-loop around a D3 statement, this should raise serious suspicion. To circumvent this you can use its powerful data binding features:

d3.selectAll("text")
  .data(d3.range(6).map(function(d) {         // data binding replaces for-loop
    return {
      x: d * 100,
      y: d * 200,
      remove: false                           // used to mark the texts for removal
    };
  }))                            
  .enter().append("text")
    .text("Hello World")
    .attr("x", function(d) { return d.x; })   // replaces myVarX
    .attr("y", function(d) { return d.y; })   // replaces myVarY
    .attr("fill", "black")
    .attr("transform", function(d){
       var bb = this.getBBox();
       // mark texts for removal based on the condition
       d.remove = (bb.x + (bb.width / (-2))) <= centerX + 5;
       return "translate(" + (bb.width / (-2)) + ", 0)";
    })
    .style("display", "block")
  .filter(function(d) { return d.remove; })   // select all texts marked for removal
    .remove();

This is the way a D3 purist would take: it's all in the data! The approach uses data objects to hold all the information for positions x and y as well as a flag remove which is used to indicate whether a text is to be removed based on some condition. Apart from removing the for-loop, this will get rid of some other variables like myVarX and myVarY, and will also integrate the block for removing some of the elements.