set element width in a grid layout code example

Example 1: css grid full width row

.child-item {
  grid-column: 1 / -1;
}

Example 2: grid css fr width of content

/* Valeurs avec un mot-clé */
grid-auto-columns: min-content;
grid-auto-columns: max-content;
grid-auto-columns: auto;

/* Valeurs de longueur */
/* Type <length>       */
grid-auto-columns: 100px;
grid-auto-columns: 20cm;
grid-auto-columns: 50vmax;

/* Valeurs proportionnelles */
/* Type <percentage>        */
grid-auto-columns: 10%;
grid-auto-columns: 33.3%;

/* Valeurs <flex> */
grid-auto-columns: 0.5fr;
grid-auto-columns: 3fr;

/* Valeurs minmax() */
grid-auto-columns: minmax(100px, auto);
grid-auto-columns: minmax(max-content, 2fr);
grid-auto-columns: minmax(20%, 80vmax);

/* Valeurs fit-content() */
grid-auto-columns: fit-content(400px);
grid-auto-columns: fit-content(5cm);
grid-auto-columns: fit-content(20%);

/* Gestion de plusieurs pistes */
grid-auto-columns: min-content max-content auto;
grid-auto-columns: 100px 150px 390px;
​​​​​​​grid-auto-columns: 10% 33.3%;
grid-auto-columns: 0.5fr 3fr 1fr;
​​​​​​​grid-auto-columns: minmax(100px, auto) minmax(max-content, 2fr) minmax(20%, 80vmax);
grid-auto-columns: 100px minmax(100px, auto) 10% 0.5fr fit-content(400px);

/* Valeurs globales */
grid-auto-columns: inherit;
grid-auto-columns: initial;
grid-auto-columns: unset;