Javascript Funky array mishap

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6 Answers

javascriptarray
90%

This is a known problem with console.log.,Instead of turning the parameter into a string when you call the method, the parameter is stored and turned into a string when it's displayed in the UI. As nothing happens in the UI while the function is running, you will see the state of the object as it is when you exit the function., Can sanitary pads be a better alternate to gauze to reduce or stop bleeding? ,So, to avoid this issue ensure that each log parameter involves the evaluation of an expression.

I'm assuming this has to do with the way that console.log() works although you're doing something a little funky when you say:

b = b.push("bb");

you should be able to just say

b.push("bb");
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88%

But now, look at the difference when we invoke obj.whoAmI() vs. our convenience reference whoAmI():,Memory Leak Example 1: Dangling references to defunct objects,Objects are kept in memory at least as long as they are accessible from any of the roots through a reference, or a chain of references.,The alternative to passing a string as the first argument to these methods is to instead pass in a function. Let’s take a look at an example.

Consider this example code snippet:

Game.prototype.restart = function() {
   this.clearLocalStorage();
   this.timer = setTimeout(function() {
      this.clearBoard(); // what is "this"?
   }, 0);
};
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72%

The articles reprinted here are not exact duplicates. They go through an editing process in conjunction with the author before being published.,Note that objects will be found only if the same reference is provided. A second argument can provide the start index at which to begin searching.,Shallow copy means that the copy will hold the same object references as the source array, which is generally a good thing. For example:,Other than that, another common use for .slice is removing the first few elements from a list of arguments, which is an array-like object that we can cast to a real array.

Furthermore, we could pass an optional second argument which will become the context (this) for each function call.

['_', 't', 'a', 'n', 'i', 'f', ']'].forEach(function(value, index, array) {
   this.push(String.fromCharCode(value.charCodeAt() + index + 2))
}, out = [])

out.join('')
// <- 'awesome'
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65%

The following example tests whether any element in the array is bigger than 10., To mimic the function of the includes() method, this custom function returns true if the element exists in the array: , true if the callback function returns a truthy value for at least one element in the array. Otherwise, false. ,A function to test for each element, taking three arguments:

// Arrow function
some((element) => {
   ...
})
some((element, index) => {
   ...
})
some((element, index, array) => {
   ...
})

// Callback function
some(callbackFn)
some(callbackFn, thisArg)

// Inline callback function
some(function callbackFn(element) {
   ...
})
some(function callbackFn(element, index) {
   ...
})
some(function callbackFn(element, index, array) {
   ...
})
some(function callbackFn(element, index, array) {
   ...
}, thisArg)
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75%

typeof null === "object" is perhaps the most common typing mistake in JavaScript, but there are others as well. A much less common but no less confusing problem is that of determining whether an object is an array. Surely, say you, this is a simple problem with a simple solution, like so:,I found this article helpful in examining some of the hacks to determine whether or not an object is "most likely" an array.,JavaScript's typeof operator is well known to have confusing behavior: typeof null === "object", and typeof null !== "null". This mistake trips up newcomers, and every so often it'll trip up a seasoned yet forgetful veteran, but we've basically grown used to it. Perhaps more important, there's a failsafe workaround: simply compare directly as v === null to eliminate null from the possibilities under consideration.,If you happen to be writing JavaScript that crosses window boundaries passing around arrays, you're out of luck trying to use flattenArray. From the MochiKit interpreter, note the instanceof Array check, with a little reformatting:

typeof null === "object" is perhaps the most common typing mistake in JavaScript, but there are others as well. A much less common but no less confusing problem is that of determining whether an object is an array. Surely, say you, this is a simple problem with a simple solution, like so:

if (o instanceof Array) {
   // Oh frabjous day!
}
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40%

JavaScript’s reduce method is one of the cornerstones of functional programming. Let’s explore how it works, when you should use it, and some of the cool things it can do.,Use it when: You have an array of amounts and you want to add them all up.,Use it when: You have a collection of items and you want to know how many of each item are in the collection.,For these examples, it would make more sense to use map or filter because they are simpler to use. The benefit of using reduce comes into play when you want to map and filter together and you have a lot of data to go over.

Use it when: You have an array of amounts and you want to add them all up.

const euros = [29.76, 41.85, 46.5];

const sum = euros.reduce((total, amount) => total + amount);

sum // 118.11
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