Let’s look a little closer at what actually happened when you put flex: 1 on those flex items in the last lesson.
This section contains a general overview of topics that you will learn in this lesson.
flex shorthand, and how to use them individually.The flex declaration is actually a shorthand for 3 properties that you can set on a flex item. These properties affect how flex items size themselves within their container. You’ve seen some shorthand properties before, but we haven’t officially defined them yet.
Shorthand properties are CSS properties that let you set the values of multiple other CSS properties simultaneously. Using a shorthand property, you can write more concise (and often more readable) stylesheets, saving time and energy.
Source: Shorthand properties on MDN
In this case, flex is actually a shorthand for flex-grow, flex-shrink and flex-basis.
In the above screenshot, flex: 1 equates to: flex-grow: 1, flex-shrink: 1, flex-basis: 0.
Very often you see the flex shorthand defined with only one value. In that case, that value is applied to flex-grow. So when we put flex: 1 on our divs, we were actually specifying a shorthand of flex: 1 1 0.
For an interactive explanation and demo of the flex shorthand, check out this Scrim:https://scrimba.com/learn/flexbox/the-flex-property-flexbox-tutorial-cGNKJTv?embed=odin,mini-header,no-big-play,no-next-up
flex-grow expects a single number as its value, and that number is used as the flex-item’s “growth factor”. When we applied flex: 1 to every div inside our container, we were telling every div to grow the same amount. The result of this is that every div ends up the exact same size. If we instead add flex: 2 to just one of the divs, then that div would grow to 2x the size of the others.
In the following example the flex shorthand has values for flex-shrink and flex-basis specified with their default values.
See the Pen flex-grow example by TheOdinProject (@TheOdinProjectExamples) on CodePen.
flex-shrink is similar to flex-grow, but sets the “shrink factor” of a flex item. flex-shrink only ends up being applied if the size of all flex items is larger than their parent container. For example, if our 3 divs from above had a width declaration like: width: 100px, and .flex-container was smaller than 300px, our divs would have to shrink to fit.
The default shrink factor is flex-shrink: 1, which means all items will shrink evenly. If you do not want an item to shrink then you can specify flex-shrink: 0;. You can also specify higher numbers to make certain items shrink at a higher rate than normal.
Here’s an example. Note that we’ve also changed the flex-basis for reasons that will be explained shortly. If you shrink your browser window you’ll notice that .two never gets smaller than the given width of 250px, even though the flex-grow rule would otherwise specify that each element should be equally sized.
See the Pen flex-shrink example by TheOdinProject (@TheOdinProjectExamples) on CodePen.
An important implication to notice here is that when you specify flex-grow or flex-shrink, flex items do not necessarily respect your given values for width. In the above example, all 3 divs are given a width of 250px, but when their parent is big enough, they grow to fill it. Likewise, when the parent is too small, the default behavior is for them to shrink to fit. This is not a bug, but it could be confusing behavior if you aren’t expecting it.
flex-basis simply sets the initial size of a flex item, so any sort of flex-growing or flex-shrinking starts from that baseline size. The shorthand value defaults to flex-basis: 0%. The reason we had to change it to auto in the flex-shrink example is that with the basis set to 0, those items would ignore the item’s width, and everything would shrink evenly. Using auto as a flex-basis tells the item to check for a width declaration (width: 250px).
Important Note About Flex-Basis:
There is a difference between the default value of
flex-basisand the way theflexshorthand defines it if noflex-basisis given. The actual default value forflex-basisisauto, but when you specifyflex: 1on an element, it interprets that asflex: 1 1 0. If you want to only adjust an item’sflex-growyou can simply do so directly, without the shorthand. Or you can be more verbose and use the full 3 value shorthandflex: 1 1 auto, which is also equivalent to usingflex: auto.
What is flex: auto?
If you noticed, we mentioned a new flex shorthand
flex: autoin the previous note. However we didn’t fully introduce it.flex: autois one of the shorthands of flex. Whenautois defined as a flex keyword it is equivalent to the values offlex-grow: 1,flex-shrink: 1andflex-basis: autoor toflex: 1 1 autousing the flex shorthand. Note thatflex: autois not the default value when using the flex shorthand despite the name being “auto” which may be slightly confusing at first. You will encounter and learn more aboutflex: autoand its potential use-cases when reading through the assignment section.
In practice you will likely not be using complex values for flex-grow, flex-shrink or flex-basis. Generally, you’re most likely to use declarations like flex: 1; to make divs grow evenly and flex-shrink: 0 to keep certain divs from shrinking.
It is possible to get fancy, and set up layouts where some columns relate to each other in a specific ratio, so it’s useful to know that you can use other values, but those are relatively rare.
This section contains questions for you to check your understanding of this lesson on your own. If you’re having trouble answering a question, click it and review the material it links to.
flex property (e.g. flex: 1 1 auto)?flex:auto?This section contains helpful links to related content. It isn’t required, so consider it supplemental.