我在输入中添加了一个默认值，并添加了一个按钮，如果macAddress的长度有效，它将调用下面这行代码：

macAddr.replace(/(.{2})/g,"$1:").slice(0,-1).toUpperCase();

代码：
第一次

好的，那么，这是我的解决方案。它过滤非十六进制，自动插入冒号，删除时跳过它们，允许插入，并处理特殊情况（比如跳过已经存在的冒号）。它很难看吗？是的，也许吧。它工作吗？是的，在我目前发现的所有情况下。我会更新任何遗漏的情况，因为它们出现了，我应该找到并修复它们。请在您自己的代码中随意使用它，赚$$$，过上好日子。

this.macForm.controls.mac.valueChanges.subscribe((mac: string) => {
            let start = this.searchField.nativeElement.selectionStart;
            let colonStartedAtRight;
            const noColons = mac.replace(/([^A-Za-z0-9])/g, '').toLowerCase();
            const isHex = (parseInt(noColons, 16).toString(16).padStart(noColons.length, ‘0’) === noColons);
            if (!isHex) { start--; }
            if (this.searchMeterForm.controls.searchMeterField.value.charAt(this.searchField.nativeElement.selectionStart) === ':') {
                colonStartedAtRight = true;
            }
            let updatedMac = mac
                .replace(/(^:|[^A-Fa-f0-9:]|:{2,})/g, '') // Restrict characters to only those in MAC addresses
                .toUpperCase();

            for (let i = 0; i < 4; i++) {
                updatedMac = updatedMac
                    .replace(/(?:^|:)([A-Fa-f0-9]{1}):/g, '$1') // Auto remove colons around single characters
                    .replace(/([A-Fa-f0-9]{2})([A-Fa-f0-9]{2}|[A-Fa-f0-9]{1})/g, '$1:$2'); // Auto insert colon every 2 characters
            }

            this.searchMeterForm.controls.searchMeterField.patchValue(
                updatedMac.substring(0, 17),
                { emitEvent: false, onlySelf: true }
            );
            const colonBeforeCount = mac.split(':').length - 1;
            const colonAfterCount = this.searchMeterForm.controls.searchMeterField.value.split(':').length - 1;
            const colonAdded = colonAfterCount > colonBeforeCount && start % 3 === 0 ? 1 : 0;
            this.searchField.nativeElement.setSelectionRange(
                start + colonAdded,
                start + colonAdded
            );
            let nowTotalColons = 0;
            for (let i = 0, length = mac.length; i < length; i++) {
                nowTotalColons += mac.charAt(i) === ':' ? 1 : 0;
            }
            if (this.searchMeterForm.controls.searchMeterField.value.charAt(this.searchField.nativeElement.selectionStart) === ':' &&
                !(this.beforeTotalColons > nowTotalColons)) {
                this.searchField.nativeElement.setSelectionRange(
                    this.searchField.nativeElement.selectionStart + 1,
                    this.searchField.nativeElement.selectionStart + 1
                );
            }
            this.beforeTotalColons = nowTotalColons;

            if (this.searchMeterForm.controls.searchMeterField.value.charAt(this.searchField.nativeElement.selectionStart - 1) === ':' &&
                colonStartedAtRight &&
                this.searchField.nativeElement.selectionStart === start) {
                this.searchField.nativeElement.setSelectionRange(
                    this.searchField.nativeElement.selectionStart + 1,
                    this.searchField.nativeElement.selectionStart + 1
                );
            }
        })