JavaScript example: Defining a variable using bitwise OR operator for encoding purposes

Question

JavaScript example: Defining a variable using bitwise OR operator for encoding purposes

Today I came across some JavaScript code that involves bitwise operations, but my knowledge on the topic is limited. Despite searching online for explanations, I'm still unable to grasp the concept. Can someone provide insight into the following code snippet?

     function createExcerpt(string, maxLength) {
          // Setting a default maximum length of 110
          maxLength = maxLength | 110;
          ...

While I understand that the pipe character represents a bitwise OR operation, I am struggling to comprehend its specific role in the given context. If providing additional details from the function would be helpful, please don't hesitate to ask.

javascript bit-manipulation bitwise-operators bitwise-or

Answer 1

Answer №1

After spotting the comment in the line above, it appears to be a simple typo.

To establish defaults, typically the logical or operator, ||, would be utilized, so most likely it should read as follows:

maxLength = maxLength || 110;

However, this approach is not ideal because if maxLength has been assigned a falsey value (such as zero), it will be replaced with the default value. This might be what you desire, though it lacks clarity.

A possibly better alternative would be the slightly lengthier but more explicit:

if (maxLength === undefined) { maxLength = 110; }

This still keeps everything on one line and defines the purpose very clearly.

If you have access to ES6 features, an even improved method would involve using default arguments within the function declaration itself:

function createExcerpt(string, maxLength = 110) {
    ...
}

Answer 2

After spotting the comment in the line above, it appears to be a simple typo.

To establish defaults, typically the logical or operator, ||, would be utilized, so most likely it should read as follows:

maxLength = maxLength || 110;

However, this approach is not ideal because if maxLength has been assigned a falsey value (such as zero), it will be replaced with the default value. This might be what you desire, though it lacks clarity.

A possibly better alternative would be the slightly lengthier but more explicit:

if (maxLength === undefined) { maxLength = 110; }

This still keeps everything on one line and defines the purpose very clearly.

If you have access to ES6 features, an even improved method would involve using default arguments within the function declaration itself:

function createExcerpt(string, maxLength = 110) {
    ...
}

Answer 3

Answer №2

It's clear that there was an error made here. The Logical OR (||) operator is supposed to be used for null coalescing, not Bitwise ORing as mentioned in the comment. If you run some tests yourself, you'll see the difference.

110 | 110 = 110
120 | 110 = 126
90 | 110 = 126
null | 110 = 110
50 | 110 = 126
200 | 110 = 238

Just by looking at a few examples, it's easy to see how confusing the results can be when using the incorrect operator with a "maxlength" argument.

Answer 4

It's clear that there was an error made here. The Logical OR (||) operator is supposed to be used for null coalescing, not Bitwise ORing as mentioned in the comment. If you run some tests yourself, you'll see the difference.

110 | 110 = 110
120 | 110 = 126
90 | 110 = 126
null | 110 = 110
50 | 110 = 126
200 | 110 = 238

Just by looking at a few examples, it's easy to see how confusing the results can be when using the incorrect operator with a "maxlength" argument.

JavaScript example: Defining a variable using bitwise OR operator for encoding purposes

Answer №1

Answer №2

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