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updateStyle(): Make it possible to update element styles for the same style object #3023

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updateStyle(): Make it possible to update element styles for the same style object #3023

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8 changes: 4 additions & 4 deletions render/render.js
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Original file line number Diff line number Diff line change
Expand Up @@ -749,16 +749,16 @@ module.exports = function() {

//style
function updateStyle(element, old, style) {
if (old === style) {
// Styles are equivalent, do nothing.
} else if (style == null) {
// The case `old` and `style` are the same string has already skipped in setAttr().
if (style == null) {
// New style is missing, just clear it.
element.style = ""
} else if (typeof style !== "object") {
// New style is a string, let engine deal with patching.
element.style = style
} else if (old == null || typeof old !== "object") {
} else if (old == null || typeof old !== "object" || old === style) {
// `old` is missing or a string, `style` is an object.
// `old` and `style` are the same object (in this case, conciliation between objects does not work well.)
element.style = ""
// Add new style properties
for (var key in style) {
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13 changes: 13 additions & 0 deletions render/tests/test-updateElement.js
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Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,19 @@ o.spec("updateElement", function() {

o(updated.dom.style.color).equals("red")
})
o("re-render element styles for the same style object", function() {
var style = {color: "gold"}
var vnode = m("a", {style: style})

render(root, vnode)

// modify the same object
style.color = "red"
var updated = m("a", {style: style})
render(root, updated)

o(updated.dom.style.color).equals("red")
})
o("setting style to `null` removes all styles", function() {
var vnode = m("p", {style: "background-color: red"})
var updated = m("p", {style: null})
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