Why Don't Arrow Functions Work in IE11, and How Can I Fix It?

Arrow Functions and IE 11 Compatibility: Understanding the Syntax Error

In the realm of JavaScript programming, arrow functions offer concise syntax for defining functions. However, these functions may not always be compatible with older browsers, including Internet Explorer 11 (IE 11).

In the case of the provided code snippet:

g.selectAll(".mainBars")
    .append("text")
    .attr("x", d => (d.part == "primary" ? -40 : 40))
    .attr("y", d => +6)
    .text(d => d.key)
    .attr("text-anchor", d => (d.part == "primary" ? "end" : "start"));

When this code is executed in IE 11, a syntax error is encountered. The underlying reason lies in the usage of arrow functions, which are introduced in ES6 (ECMAScript 2015) and not supported by IE 11.

Overcoming the Compatibility Issue

To make the code compatible with IE 11, the arrow functions need to be replaced with traditional function declarations. The corresponding ES5 code would look similar to the following:

g.selectAll(".mainBars").append("text").attr("x", function (d) {
  return d.part == "primary" ? -40 : 40;
}).attr("y", function (d) {
  return +6;
}).text(function (d) {
  return d.key;
}).attr("text-anchor", function (d) {
  return d.part == "primary" ? "end" : "start";
});

By utilizing traditional function declarations, this modified code will successfully execute in IE 11, preserving the intended functionality. It's important to note that traditional functions have different rules for binding the this keyword compared to arrow functions, so these differences should be considered when transitioning code between versions of JavaScript.

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