JS 中数据类型的转换
在 JS 中可以强制转换目标的数据类型(显示转换)
把目标转成字符串
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<script>
console.log("String(11): " + String(11));
console.log("String(true): " + String(true));
console.log("String(false): " + String(false));
console.log("String(undefined): " + String(undefined));
console.log("String(null): " + String(null));
console.log("String([]): " + String([]));
console.log("String({}): " + String({}));
</script>
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案例源码
图片中把空数组转换为字符串，实际上是空字符串。
把目标转成数字
JS 会把目标先转成字符串，再尝试转为数字
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<script>
console.log("Number('11'): " + Number("11"));
console.log("Number('abc'): " + Number("abc"));
console.log("Number(''): " + Number(""));
console.log("Number(true): " + Number(true));
console.log("Number(false): " + Number(false));
console.log("Number(undefined): " + Number(undefined));
console.log("Number(null): " + Number(null));
console.log("Number([]): " + Number([]));
console.log("Number({}): " + Number({}));
</script>
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案例源码
把目标转成布尔值
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<script>
console.log("Boolean('11'): " + Boolean("11"));
console.log("Boolean('abc'): " + Boolean("abc"));
console.log("Boolean(''): " + Boolean(""));
console.log("Boolean(NaN): " + Boolean(NaN));
console.log("Boolean(0): " + Boolean(0));
console.log("Boolean(1): " + Boolean(1));
console.log("Boolean(undefined): " + Boolean(undefined));
console.log("Boolean(null): " + Boolean(null));
console.log("Boolean([]): " + Boolean([]));
console.log("Boolean({}): " + Boolean({}));
</script>
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一共有 5 中类型转成布尔值后是 false: 0 '' undefined null NaN， 其他类型转换成布尔值都是true
案例源码
