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March 14, 2017 02:37
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Makes sure a given element is in the visible area of its scroll container;
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| function ensureVisibility(e, c) { | |
| let e0 = e.offsetTop | |
| let eD = e.clientHeight | |
| let e1 = e0 + eD | |
| let c0 = c.scrollTop | |
| let cD = c.clientHeight | |
| let c1 = c0 + cD | |
| let visible = e0 > c0 && e1 < c1 | |
| if (!visible) { | |
| if (e0 <= c0) { | |
| // Stick at container top | |
| c.scrollTop = e0 | |
| } else { | |
| // Stick at container bottom | |
| c.scrollTop = e1 - cD | |
| } | |
| } | |
| } |
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