Clean up utils.js to reduce bundle size

[dgirardi]

Type of issue

improvement

Description

utils.js is simultaneously the largest and least maintained file in the codebase. It can be improved in at least two ways:

• move logic that is not needed by core into libraries, so that it ends up only in bundles with modules that actually need it. As example, this:
  

  Prebid.js/src/utils.js

  Lines 657 to 668 in 3c70ac7

  	export function getValueString(param, val, defaultValue) {
  	if (val === undefined || val === null) {
  	return defaultValue;
  	}
  	if (isStr(val)) {
  	return val;
  	}
  	if (isNumber(val)) {
  	return val.toString();
  	}
  	internal.logWarn('Unsuported type for param: ' + param + ' required type: String');
  	}

  
  is only needed by a few appnexus-like bidders.
• refactor usage of "shim" utility functions that are now part of vanilla javascript. For example:
  

  Prebid.js/src/utils.js

  Lines 68 to 76 in 3c70ac7

  	export let bind = function(a, b) { return b; }.bind(null, 1, uniqueRef)() === uniqueRef
  	? Function.prototype.bind
  	: function(bind) {
  	var self = this;
  	var args = Array.prototype.slice.call(arguments, 1);
  	return function() {
  	return self.apply(bind, args.concat(Array.prototype.slice.call(arguments)));
  	};
  	};

  
  

  Prebid.js/src/utils.js

  Lines 470 to 479 in 3c70ac7

  	export function _map(object, callback) {
  	if (isEmpty(object)) return [];
  	if (isFn(object.map)) return object.map(callback);
  	var output = [];
  	_each(object, function (value, key) {
  	output.push(callback(value, key, object));
  	});
  	return output;
  	}

  
  and many others.

[pm-harshad-mane]

Isn't dead code elimination taken care of at the build generation time?

[dgirardi]

@pm-harshad-mane, that is correct, but this issue is not about dead code. To the build logic, dead code is code that can be statically determined to be unreachable. If some code in core is reachable only by a module you don't need, it's still kept in the output - unless you run a custom build where that module is not compiled at all.