51 lines
1.2 KiB
JavaScript
51 lines
1.2 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @format
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* @flow
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*/
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'use strict';
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type truncateOptions = {
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breakOnWords: boolean,
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minDelta: number,
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elipsis: string,
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};
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const defaultOptions = {
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breakOnWords: true,
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minDelta: 10, // Prevents truncating a tiny bit off the end
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elipsis: '...',
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};
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// maxChars (including ellipsis)
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const truncate = function(
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str: ?string,
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maxChars: number,
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options?: truncateOptions,
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): ?string {
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options = Object.assign({}, defaultOptions, options);
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if (
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str &&
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str.length &&
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str.length - options.minDelta + options.elipsis.length >= maxChars
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) {
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// If the slice is happening in the middle of a wide char, add one more char
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const extraChar =
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str.charCodeAt(maxChars - options.elipsis.length) > 255 ? 1 : 0;
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str = str.slice(0, maxChars - options.elipsis.length + 1 + extraChar);
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if (options.breakOnWords) {
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const ii = Math.max(str.lastIndexOf(' '), str.lastIndexOf('\n'));
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str = str.slice(0, ii);
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}
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str = str.trim() + options.elipsis;
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}
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return str;
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};
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module.exports = truncate;
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