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51 lines
1.3 KiB
JavaScript
51 lines
1.3 KiB
JavaScript
"use strict";
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module.exports = function immutableDeepMerge(object1, object2) {
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let hasChanges = false;
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let changedProperties = { };
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let deletedProperties = [];
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if (object2 != null) {
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for (let key of Object.keys(object2)) {
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let value = object2[key];
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let originalValue = object1[key];
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if (value === Delete) {
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deletedProperties.push(key);
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hasChanges = true;
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} else {
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let transformedValue;
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let normalizedValue = (typeof value === "function")
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? value(originalValue)
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: value;
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if (typeof normalizedValue === "object" && normalizedValue !== null) {
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// NOTE: We default to an empty object for the original value because from the perspective of a deep-merge, any nested paths required by the new input that don't exist in the original input should be imagined into existence.
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transformedValue = immutableDeepMerge(originalValue ?? {}, normalizedValue);
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} else {
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transformedValue = normalizedValue;
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}
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changedProperties[key] = transformedValue;
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if (transformedValue !== originalValue) {
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hasChanges = true;
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}
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}
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}
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}
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if (hasChanges) {
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let merged = { ... object1, ... changedProperties };
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for (let property of deletedProperties) {
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delete merged[property];
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}
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return merged;
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} else {
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return object1;
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}
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};
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