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how to use style() method in D3 js

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by chandramouliprabuoff dot icon Updated: Jan 29, 2024

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D3.js, quick for Data-Driven Documents, is an effective JavaScript library. It's designed for creating dynamic and interactive data visualizations in web browsers. D3 is a JavaScript library.

It provides a set of tools and functions. Developers use them to bind data to HTML or SVG elements. Then, they apply data-driven transformations to the document. Styling plays a crucial role in creating appealing and effective data visualizations. The primary purpose of D3.js is to manipulate the DOM based on data. The visual presentation of the information is important. Effective styling enhances the readability of charts and graphs. This makes the insights more accessible to the audience. Choosing matching colors, lining things up, and using good fonts makes everything look good and professional. D3.js uses CSS styles to enhance the visual presentation of data visualizations. 


  • D3 provides selection methods. Developers can target specific elements in the Document Object Model (DOM). 
  • D3's basic syntax involves selecting elements. Then, chaining methods for manipulation. 
  • Usage of the selectAll Method: In D3, you can use the selectAll method to target and select many elements in the DOM. 
  • You can give special looks to chosen things in D3 by using different styles and names for them. D3 offers the style method. Users apply styles to selected elements. 
  • D3 allows for dynamic styling based on data values. This adds a layer of flexibility to visualizations. 
  • D3's style method lets you change how things look. This flexibility makes it easy to change styles. You can adjust different style aspects like color or size. 
  • When you style things in D3, it's like putting on a nice outfit for your data, making it pleasing to the eye. 
  • You can keep a similar look by using CSS classes and special tags. They make sure everything looks similar. It's like using the same color and font to keep everything in harmony. 

For example, consider a scenario with a bar chart representing data points. You can use D3 to select all the bars. Then, bind data to them and set the height of each bar proportional to its corresponding data value. This dynamic styling conveys the significance of each data point, making it easier to understand. D3 also supports styling using inline styles through the style attribute. This can be particularly useful when you want to apply styles to individual SVG elements within your visualizations. 


Consistent Styling with Class Attributes: 

  1. D3.js enables developers to use class attributes for consistent styling. They can apply the same styling across many HTML or SVG elements within a visualization. 
  2. By assigning a common class to related elements, developers can ensure a uniform and cohesive visual appearance. 

CSS Classes in Selection and Chaining: 

  1. D3's selection methods, like selectAll, can target and manipulate CSS classes. They can be helpful to select and manipulate specific groups of elements. 
  2. You can apply chaining methods to these selections, which streamlines the styling process. 


In conclusion, D3.js empowers developers to create compelling data visualizations. It does this by providing a robust set of tools for manipulating the DOM based on data. Styling facilitated by CSS is integral to the process. It contributes to the effectiveness and aesthetic appeal of the visualizations. Developers can improve their D3.js visualizations. They can do this by understanding the basic syntax and incorporating styling techniques. This will help them communicate insights to their audience. 

Fig 1: Preview of the output that you will get on running this code from your IDE.

Code

Changing the line style in d3js for every segment?

Lines of Code : 257dotLicense : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries : 
actualRaw.map(line => {
    actual.push({
        date: line.date,
        points: line.done,
        class: 'la'
    });
    actual.push({
        date: line.date,
        points: line.done + line.added,
        class: 'ln',
        added: line.added//this one here...
    });
})

var redLines = chart.selectAll(null)
    .data(actual.filter(function(d) {
        return d.added
    }))
    .enter()
    .append("line")
    .attr("x1", function(d) {
        return x(d.date)
    })
    .attr("x2", function(d) {
        return x(d.date)
    })
    .attr("y1", function(d) {
        return y(d.points)
    })
    .attr("y2", function(d) {
        return y(d.points - d.added)
    })
    .style("stroke", "red");

<head>
  <title>Burn baby burn</title>
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style type="text/css">
    .chart {
      border: 1px solid black;
    }
    
    .chart div {
      font: 10px sans-serif;
      background-color: steelblue;
      text-align: right;
      padding: 3px;
      margin: 1px;
      color: white;
    }
    
    .chart rect {
      stroke: white;
      fill: steelblue;
    }
    
    .axis path,
    .axis line {
      fill: none;
      stroke: #000;
      shape-rendering: crispEdges;
    }
    
    .line {
      fill: none;
      stroke-width: 2px;
    }
    
    .line.ideal {
      stroke: steelblue;
    }
    
    .la {
      fill: none;
      stroke-width: 2px;
      stroke: green;
    }
    
    .ln {
      fill: none;
      stroke: red;
      stroke-width: 4px;
    }
  </style>
</head>

<body>
  <h1>Burn Chart</h1>
  <script type="text/javascript">
    var margin = {
        top: 20,
        right: 20,
        bottom: 30,
        left: 50
      },
      width = 960 - margin.left - margin.right,
      height = 500 - margin.top - margin.bottom;
    var x = d3.scaleTime()
      .range([0, width]);
    var y = d3.scaleLinear()
      .range([height, 0]);
    var ideal = [{
      date: new Date(2017, 1, 1),
      points: 50
    }, {
      date: new Date(2017, 12, 31),
      points: 0
    }];
    var actualRaw = [{
      date: new Date(2017, 1, 1),
      added: 0,
      done: 50
    }, {
      date: new Date(2017, 1, 15),
      added: 10,
      done: 40
    }, {
      date: new Date(2017, 2, 1),
      added: 0,
      done: 40
    }, {
      date: new Date(2017, 3, 1),
      added: 20,
      done: 30
    }, {
      date: new Date(2017, 4, 1),
      added: 10,
      done: 20
    }, {
      date: new Date(2017, 5, 1),
      added: 5,
      done: 10
    }, {
      date: new Date(2017, 6, 1),
      added: 0,
      done: 10
    }, {
      date: new Date(2017, 7, 1),
      added: 5,
      done: 10
    }, {
      date: new Date(2017, 8, 1),
      added: 0,
      done: 10
    }, {
      date: new Date(2017, 9, 1),
      added: 20,
      done: 20
    }, {
      date: new Date(2017, 10, 1),
      added: 0,
      done: 10
    }, {
      date: new Date(2017, 11, 1),
      added: 5,
      done: 10
    }, {
      date: new Date(2017, 12, 1),
      added: 0,
      done: 0
    }];
    var actual = [];
    actualRaw.map(line => {
      actual.push({
        date: line.date,
        points: line.done,
        class: 'la'
      });
      actual.push({
        date: line.date,
        points: line.done + line.added,
        class: 'ln',
        added: line.added
      });
    })
    var idealLine = d3.line()
      .x(function(d) {
        return x(d.date);
      })
      .y(function(d) {
        return y(d.points);
      });
    var actualLine = d3.line()
      .x(function(d) {
        return x(d.date);
      })
      .y(function(d) {
        return y(d.points);
      });
    x.domain(d3.extent(ideal, function(d) {
      return d.date;
    }));
    y.domain(d3.extent(actual, function(d) {
      return d.points;
    }));
    var xAxis = d3.axisBottom()
      .scale(x)
      .tickFormat(d3.timeFormat("%b %d"));
    var yAxis = d3.axisLeft()
      .scale(y);
    var chart = d3.select("body").append("svg")
      .attr("class", "chart")
      .attr("width", width + margin.left + margin.right)
      .attr("height", height + margin.top + margin.bottom)
      .append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
    // Create the x-axis
    chart.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);
    // Create the y-axis
    chart.append("g")
      .attr("class", "y axis")
      .call(yAxis)
      .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Points");
    // Paint the ideal line
    chart.append("path")
      .datum(ideal)
      .attr("class", "line ideal")
      .attr("d", idealLine);
    var counter = 0;
    // Paint the actual line
    chart.append("path")
      .datum(actual)
      .attr("class", function(d, i) {
        return 'line ' + d[i].class;
      })
      .attr("d", actualLine);

    var redLines = chart.selectAll(null)
      .data(actual.filter(function(d) {
        return d.added
      }))
      .enter()
      .append("line")
      .attr("x1", function(d) {
        return x(d.date)
      })
      .attr("x2", function(d) {
        return x(d.date)
      })
      .attr("y1", function(d) {
        return y(d.points)
      })
      .attr("y2", function(d) {
        return y(d.points - d.added)
      })
      .style("stroke", "red")
      .style("stroke-width", 4);
  </script>
</body>

Instruction

  1. 1.Install Visual Studio Code IDE on your computer.
  2. Create a new HTML file.
  3. Copy the code using the 'Copy' button and create an HTML tag then paste the code inside the tag into that HTML file.
  4. Copy the controller.js code and paste in the JS file created.
  5. Create a script tag inside the body tag Then keep the function lines inside the script tag(refer to preview as well).
  6. ⁠Add the script tag below the div tag.
  7. Save and run the HTML file directly from the file location to generate the output


I found this code snippet by searching for 'how to use style() method in D3 js' .you can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created in Visual Studio Code 1.75.1.


Using this solution, we are able to process form using angular js with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to use style() method in D3 js

FAQ 

1. How does the property function work in D3 js style ()? 


You can use the style () function in D3.js to apply or change CSS styles to selected elements. You need to provide two arguments for the function. The arguments are the CSS property that requires modification. It also takes a callback function or a constant value for the new style. 


2. Can you use text content in combination with SVG elements when using D3 js style()? 


Yes, D3.js allows for the combination of text content with SVG elements when using the style () function. For example, you can use style ('fill', 'red') to set the fill color of an SVG element. You can also use style ('font-size', '12px') to set the font size of text content within that element. 


3. In what ways can JavaScript be utilized within the D3 js style () function? 


JavaScript can be utilized within the style () function in several ways. You can use JavaScript variables or expressions to set CSS property values. For instance, style ('width', function(d) {return d * 10 + 'px';}) sets the width based on the data. 


4. What is the role of the current DOM element when applying styles with D3 js style ()? 


The current DOM element refers to the element(s) selected by D3.js at the point of applying the style () function. Changing the look of things with styles in D3 makes the selected elements look different on the webpage. It's like giving them a new appearance or a fresh coat of paint. 


5. How does D3 js style () handle specified attributes for different elements? 


The style () function in D3.js handles specified attributes for different elements. It allows developers to target specific elements and apply styles. For instance, you can apply the style ('fill', 'blue') method to an SVG element to set its fill color. You can also use style ('font-size', '14px') to set the font size of a text element within the SVG. 

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