39 lines
936 B
TypeScript
39 lines
936 B
TypeScript
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// 判断是否为字符串
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typeof '' === 'string';
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// 判断字符串是否包含子串，区分大小写
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'Blue Whale'.includes('blue'); // returns false
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'blue ss'.indexOf('blue');
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// str.substring(indexStart[, indexEnd])
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// 向下取整 floor
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Math.floor( 45.95); // 45
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// 向上取整 ceil
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Math.ceil(.95) // 1
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// 给定数字的值四舍五入到最接近的整数。
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Math.round(20.49); //20
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Math.round(20.5); //21
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// For iterating on keys of Arrays, Strings, or Objects, use for .. in :
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const yourobject = {}
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for (let key in yourobject) {
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console.log(key, yourobject[key]);
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}
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// With ES6, if you need both keys and values simultaneously, do
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for (let [key, value] of Object.entries(yourobject)) {
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console.log(key, value);
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}
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// To avoid logging inherited properties, check with hasOwnProperty :
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for (let key in yourobject) {
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if (yourobject.hasOwnProperty(key)) {
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console.log(key, yourobject[key]);
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}
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}
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