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An ES2015 spec-compliant shim. Invoke its "shim" method to shim if it is unavailable. Note: Function#name requires a true ES5 environment - specifically, one with ES5 getters.

This package implements the es-shim API interface. It works in an ES5-supported environment and complies with the spec.

Most common usage:


var functionName = require('');
var assert = require('assert');

assert.equal(functionName(function foo() {}), 'foo');

assert.equal(function foo() {}.name, 'foo');

Supported engines

Automatically tested in every minor version of node.

Manually tested in:

  • Safari: v4 - v15 (4, 5, 5.1, 6.0.5, 6.2, 7.1, 8, 9.1.3, 10.1.2, 11.1.2, 12.1, 13.1.2, 14.1.2, 15.3, 15.6.1)
  • Chrome: v15 - v81, v83 - v106(every integer version)
    • Note: This includes Edge v80+ and Opera v15+, which matches Chrome
  • Firefox: v3, v3.6, v4 - v105 (every integer version)
    • Note: in v42 - v63, Function.prototype.toString throws on HTML element constructors, or a Proxy to a function
    • Note: in v20 - v35, HTML element constructors are not callable, despite having typeof function
  • IE: v6 - v11(every integer version
  • Opera: v11.1, v11.5, v11.6, v12.0, v12.1, v12.14, v12.15, v12.16, v15+ v15+ matches Chrome


Simply clone the repo, npm install, and run npm test

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  • ljharb