Steps:

• Pass two strings word and anagram
• Iterate over first string word, get character at i
• If character present in anagram, then remove character from anagram
• Iterate until anagram is empty

function isAnagram(word, anagram) {
    if (word.length !== anagram.length) {
        return false;
    }
    for (let i = 0; i < word.length; i++) {
        let c = word[i];
        let index = anagram.indexOf(c);
        if (index === -1) {
            return false;
        }
        anagram = anagram.substring(0, index) + anagram.substring(index + 1, anagram.length);
    }
    return anagram.length === 0;
}

isAnagram('hello', 'olleh');

References:

• How to check if two Strings are Anagrams in Java

The top and bottom margins of blocks are sometimes collapsed into a single margin whose size is the largest of the individual margins (or just one of them, if they are equal), a behavior known as margin collapsing.

References:

• What You Should Know About Collapsing Margins
• The Rules of Margin Collapse
• Mastering margin collapsing

ECMAScript is a language specification and JavaScript is the implementation of that specification.

ECMAScript is standardised by Ecma International.

The Ecma TC39 committee is responsible for evolving the ECMAScript programming language and authoring the specification. Changes to the language are developed by way of process. There are five stages, a strawperson stage, and 4 “maturity” stages. The TC39 committee must approve accetance for each stage.

References:

• What’s the difference between JavaScript and ECMAScript?
• What’s The Difference Between JavaScript And ECMAScript
• ECMAScript
• The TC39 Process

The CSS box model defines how the different parts of a box - margin, border, padding, and content - work together to create a box that can be seen on the page.

Parts of a box

• Content box - The area where content is displayed, which can be sized using properties like width and height.
• Padding box - The padding sits around the content as white space, its size is controlled using padding and related properties.
• Border box - The border box wraps the content and any padding. Its sizing and style can be controlled using border and related properties.
• Margin box - The margin is the outermost layer, wrapping the content, padding and border as whitespace between this box and other elements. Its size can be controlled using margin and related properties.

Standard CSS box model

In the standard box model, if a box is given width and height attribute, this defines the width and height of the content box.

Alternative CSS box model

Using this model, any width is the width of the visible box on the page, therefore the content area width is that the width minux the width for the padding and border.

References:

• Introduction to the CSS basic box model
• The box model
• The CSS Box Model

HTTP Cache improves performance of web sites and applications by reusing previously fetchted resources.

Cache-Control header

The server can return a Cache-Control directive to specify how, and for how long, the browser and other intermediate caches should cache the individual response.

• No caching Cache-Control: no-store This instructs the browser and other intermediate caches (like CDNs) to never store any version of the file.

• Cache but revalidate Cache-Control: no-cache This instructs the browser that it must revalidate with the server every time before using a cached version of the URL.

• Private and public caches Cache-Control: private Browser can cache the file but intermediate caches cannot. Cache-Control: public The response can be stored by any cache.

• Expiration Cache-Control: max-age=31536000 The maximum amount of time in which a resource will be considered fresh. This directive is relative to the time of request, and overrides the Expires header (if set).

• Validation Cache-Control: must-revalidate The cache must verify the status of stale resources before using it and expired ones should not be used.

ETags

The ETag (or Entity Tag) works in a similar way to the Last-Modified header except its value is a digest of the resources contents (for instance, an MD5 Hash). This allows the server to identify if the cached contents of the resource are different to the most recent version. If the Etag header was part of the response for a resource, the client can issue an If-None-Match in the header of future requests - in order to validate the cached resource.

Last-Modified

This header servers the same purpose as ETag, but uses a time-bsaed strategy to determine if a resource has changed, as opposed to the content-based strategy of ETag. If the Last-Modified header is present in a response, then the client can issue an If-Modified-Since request header to validate the cached document.

References

• HTTP caching
• HTTP Cache
• Increasing Application Performance with HTTP Cache Headers